On April 7, the Singapore-based ISEAS-Yusof Ishak Institute released survey results from Southeast Asian experts across business, government, and academia. Below is a summary of findings on the South China Sea.

ASEAN respondents' top concern is China's encroachment in the EEZs and continental shelves of Southeast Asia's littoral states (51.7%), especially among claimant states such as Vietnam, the Philippines, and Brunei. The risk of an accidental confrontation between an ASEAN member state and China that could result in a political crisis ranks second (45.2%), with particularly high concern in Indonesia, Timor-Leste, Laos, and Cambodia—showing anxiety beyond claimant states. Broader concerns include China's militarisation and assertive actions (37.9%) and a direct military confrontation between the US and China (36.8%).

As in last year, the dominant view among ASEAN respondents is that the South China Sea Code of Conduct (COC) must be aligned with international law, including UNCLOS (40.8%). Support for this is strongest in Vietnam, Timor-Leste, and the Philippines. At the same time, 19.3% worry the COC will prevent other powers from conducting military activities and energy exploration with ASEAN member states in the South China Sea, potentially limiting security partnerships. Another 16.5% believe it will not resolve territorial disputes but will help reduce tensions and manage the dispute. Overall scepticism about the COC's effectiveness remains limited (12.3%).

On April 6, Indonesia recovered what is believed to be a Chinese underwater drone in the Lombok Strait, a key alternative route if the Strait of Malacca is disrupted. The cylindrical device bore Chinese characters and the CSIC logo, the world's largest shipbuilding conglomerate.

Chinese unmanned underwater vehicles (UUVs) have seen a rapid expansion in their presence and deployment in recent years under Beijing's military-civil fusion strategy, raising concerns among neighboring countries that they may be collecting sensitive data within EEZ.

In recent years, fishermen in Indonesia, Vietnam, and the Philippines have repeatedly found UUVs in regional waters, highlighting growing concerns over surveillance activity and maritime security.

In the South China Sea, China is tightening control of the entrance to Scarborough Shoal by deploying ships and installing a 352‑meter floating barrier on April 10–11, the Philippine coast guard said. Six Chinese maritime militia vessels were seen inside the shoal and three outside, blocking the entrance. Photos from April 10–11 show fishing boats and the barrier, while satellite imagery indicates a probable Chinese naval or coast guard vessel nearby. The Philippine Navy reported 10 Chinese coast guard vessels at the shoal from April 5 to 12.

Scarborough is one of Asia's most disputed maritime sites. As China's presence grows, the Philippines and the United States have increased military cooperation. Thousands of troops will hold large‑scale exercises across the Philippines this month, including areas about 120 nautical miles from the shoal. Diplomats say the drills and tensions are being closely watched amid concerns that China could act while the U.S. is focused on the Iran conflict and reopening the Strait of Hormuz.

On April 15, the JCG confirmed the Chinese oceanographic research vessel "Kexue" extending what appeared to be a wire into the water in Japan's EEZ, approximately 74 kilometers north of Ishigakijima Island in Okinawa Prefecture. The JCG demanded that the activity cease, stating that research conducted without Japan's consent is not permitted. However, the vessel continued operating in Japan's EEZ on April 16. This is the first confirmed activity by a Chinese research vessel in Japan's EEZ since similar activities were observed off the Senkaku Islands from March 30 to April 2.

On April 16, Vice Minister for Foreign Affairs of Japan held an exchange of views with NATO Permanent Representatives and others in Tokyo.

Japan's Vice Minister stated his intention to strengthen cooperation with NATO, a partner sharing fundamental values and strategic interests, and to develop concrete cooperation, under the shared recognition that the security of the Euro-Atlantic and Indo-Pacific is closely linked. In response, Permanent Representatives expressed the same view and their intention to further develop Japan–NATO and NATO–IP4 relations. They exchanged frank views on regional issues, including challenges in the Indo-Pacific such as those related to China.

On April 16, Minister for Foreign Affairs of Japan received a courtesy call from NATO Permanent Representatives and others in Tokyo.

Japan's Minister pointed out that the security of the Euro-Atlantic and the Indo-Pacific is inseparable and that cooperation with allies and like-minded countries is growing in importance, amid a rapidly changing international situation. He expressed hope that Permanent Representatives would deepen their understanding of the severe security environment surrounding Japan and the Indo-Pacific. In response, Permanent Representatives likewise recognized the growing importance of Japan–NATO cooperation and expressed their intention to further develop it and build concrete cooperation. They exchanged frank views on regional issues, including challenges in the Indo-Pacific such as those related to China.

Monthly Statistics on Scrambles（March）

The Japan Joint Staff released its monthly statistics on scrambles. In March, the Japan Air Self Defense Force (JASDF) conducted 52 scrambles. The most scrambles were against Russian aircraft (31 times), followed by Chinese aircraft (21 times).

Statistics on Scrambles Conducted in Fiscal Year 2025

The Japan Joint Staff released its statistics on scrambles conducted in FY2025 (April 1, 2025 to March 31, 2026). The total number of scrambles during this period was 595. Including estimates, approximately 61% of the scrambles were in response to Chinese aircraft, approximately 36% to Russian aircraft, and approximately 3% to others.

During the same period, the following incidents occurred:

– In May, a violation of Japan's airspace occurred when a helicopter was launched from a China Coast Guard vessel after it entered Japan's territorial waters near the Senkaku Islands.
– In December, for the first time, a Chinese aircraft carrier operated in the Pacific Ocean from the waters east of Okinawajima Island to those east of Amami Oshima Island. During this operation, an incident occurred in which J-15 fighter aircraft launched from the carrier intermittently illuminated JASDF F-15 fighter aircraft with its radar while they were responding to the intruding aircraft. Later that month, Chinese and Russian bombers were confirmed to have conducted a joint long-range flight from the East China Sea, through the area between Okinawajima Island and Miyakojima Island, and into the Pacific Ocean, extending to the waters off Shikoku.

On April 17, NATO Permanent Representatives and others visiting Japan paid a visit to the Ministry of Defense of Japan.

Japan's Minister emphasized that, as the security of the Euro-Atlantic and Indo-Pacific regions becomes increasingly interconnected, strengthening cooperation between Japan and NATO, NATO and IP4, and individual NATO member states is more important than ever. He reaffirmed Japan's commitment to advancing collaboration at both bilateral and multilateral levels.

In light of the increasingly severe security environment and the growing linkage between the two regions, the Vice Minister for International Affairs briefed participants on Japan's security situation and defense policy.

China has established multiple warning airspace zones (NOTAMs) over the East China Sea and the Yellow Sea for 40 days through May 6, without disclosing the reason. The move has raised speculation about possible military exercises and signaling to Japan, and Chinese military movements are being closely monitored. Reports indicate China has deployed around 100 vessels in the East and South China Seas, raising concerns this could lead to exercises based on past patterns. However, no exercises have been announced, and some analysts say large-scale exercises may be unlikely ahead of a planned visit by the U.S. president.

On April 18, Japan-Australia Defense Ministerial Meeting was held in Melbourne. The Ministers confirmed to further strengthen Japan-Australia defense cooperation. They released a joint statement after the meeting.

In their joint statement, the two countries reaffirmed their commitment to information‑sharing and to working with partners to uphold regional security based on rules rather than force, noting that Australia–Japan cooperation is vital for regional peace and stability.

They expressed serious concerns about the East and South China Seas and opposed unilateral actions, including coercion, unlawful maritime claims, militarisation of disputed areas, and unsafe conduct by Chinese maritime forces. They also reaffirmed the importance of freedom of navigation, international law including UNCLOS, and the binding nature of the 2016 Arbitral Tribunal Award.

They reaffirmed that peace and stability in the Taiwan Strait are essential and opposed unilateral attempts to change the status quo, calling for dialogue instead of coercion or force.

They also reiterated their intention to work with the United States, key partners and regional institutions such as ASEAN to strengthen regional resilience and uphold a free and open Indo‑Pacific, stressing the importance of their trilateral partnership with the United States and deeper defence cooperation.

They reaffirmed support for Pacific partners and their efforts to strengthen regional resilience through cooperation with Pacific‑led institutions, and noted progress in Maritime Cooperative Activities with the Philippines and the United States.

China said on April 17 that a New Zealand P-8A patrol aircraft conducted close-in reconnaissance and harassment in the Yellow and East China seas, undermining China's security, raising risks of miscalculation, and disrupting civil aviation.

New Zealand on April 18 defended a patrol flight near China, saying its aircraft was monitoring North Korean sanctions evasion under UN Security Council resolutions. It said the crew acted professionally, followed international law, and was part of a longstanding deployment enforcing UN sanctions.

A Japan Maritime Self-Defense Force (JMSDF) destroyer passed through the Taiwan Strait on April 17, the first such transit since Prime Minister Takaichi's remarks on a Taiwan contingency last November. Sources said the move aimed to uphold freedom of navigation and seek dialogue with China to improve bilateral ties.

This was the fourth JMSDF transit after those in September 2024, February 2025, and June 2025. The destroyer is heading to the South China Sea for joint drills with the U.S. and the Philippines, with the timing likely chosen to avoid Chinese propaganda. Since China's backlash over her remark, Takaichi has briefed major leaders on Japan's stance and ties with China. After these efforts, she has apparently decided to send another vessel through the strait.

On April 17, China said it had lodged a protest, calling the move a serious threat to its sovereignty, security, and bilateral ties.

On April 18, a Chinese oceanographic research vessel was spotted extending a wire-like object into the ocean within Japan's EEZ around the Senkaku Islands, about 106 kilometers north-northwest. The JCG urged it to stop the unauthorized survey in waters off Okinawa Prefecture, and it left the EEZ six hours later.

On April 20, the Philippines and the United States kicked off their annual Balikatan military exercise, with Japan's Self-Defense Forces fully participating for the first time. Japan had taken part as an observer since 2012, while a defense pact with the Philippines that took effect last year expanded the scope of activities in which it can participate. A total of 17,000 personnel from seven countries including Australia, Canada, France and New Zealand are joining the exercise, which runs until May 8.

Japan is sending 1,400 personnel, along with three ships and two aircraft, and plans to test-fire a Type-88 guided missile. A Philippine military official said the drill sends a "clear and unmistakable message that security is shared" and highlights partnership as a key advantage, while an SDF official said it will contribute to enhancing capabilities and deterring unilateral changes to the status quo by force.

On April 19, the JMSDF confirmed one Chinese Luyang III class destroyer (hull number 133) and one Chinese Jangkai II class frigate (hull number 577) sailing east in waters 60km southwest of Yokoatejima Island (Kagoshima Prefecture). These vessels sailed northeast through waters between Amami Oshima Island (Kagoshima Prefecture) and Yokoatejima Island and navigated to the Pacific Ocean.

China deployed warships for drills in the western Pacific as the US, the Philippines and Japan launched joint exercises, Balikatan, on April 20, underscoring rising tensions with Tokyo.

China sent a naval group led by the destroyer Baotou through waters between Amami Oshima island and Yokoate island for Western Pacific training, the PLA Eastern Theatre Command said on April 19. The drills were described as routine and not directed at any country, and are designed to test the forces' far-seas operational capabilities. The move highlights China's growing naval activity and is the first time China has announced a transit through the Yokoate Waterway, which lies closer to Japan than the commonly used Miyako Strait.

China's drills came days after it criticised Japan for sending a warship through the Taiwan Strait. On April 17, Beijing called the Japanese vessel's passage "provocative" and lodged a formal protest.

Japan has recently confirmed that China has installed a new structure west of the Japan–China equidistance line in the East China Sea. Japan finds it regrettable that China is engaging in unilateral development while the EEZ and continental shelf remain undelimited.

The Director-General of the Asian and Oceanian Affairs Bureau issued a strong protest to the Deputy Chief of Mission of the Chinese Embassy and urged China to promptly resume negotiations on the implementation of the June 2008 Agreement on joint development of East China Sea resources.

China has accelerated its resource development in recent years, and Japan has confirmed 23 structures on the Chinese side of the equidistance line. Japan maintains that maritime delimitation should be based on this line.

On April 20, Japan-UK Foreign Ministers' Strategic Dialogue was held in Tokyo.

Japan's minister stressed the growing importance of cooperation with the UK, an "Enhanced Global Strategic Partner," amid a shifting international order. The UK minister agreed, calling for closer ties.

They shared the view that Euro-Atlantic and Indo-Pacific security are inseparable and agreed to accelerate the Global Combat Air Programme (GCAP). They discussed Indo-Pacific issues, including China, and cooperation in international fora, and agreed to continue working in close coordination.

Chinese aircraft carrier Liaoning sailed through the Taiwan Strait on April 20, days after a Japan Self-Defense Force vessel did so, Taiwan's Defense Ministry said. It added that Taiwan's military is "maintaining close surveillance."

On April 22, Japan-New Zealand Summit Telephone Meeting was held.

They concurred on further deepening bilateral relations, including security cooperation, strengthening multi-layered cooperation among like-minded countries, and working toward the realization of a Free and Open Indo-Pacific (FOIP), while maintaining close communication.

The Philippines relies on the Middle East for over 90% of its crude oil, raising concerns that tensions in Iran could worsen fuel shortages. President Marcos declared a national energy emergency on March 24 and is seeking closer energy cooperation with China, including possible talks on joint oil and gas development in disputed waters.

China appears to be making a change in the Philippines' stance toward China a precondition for cooperation, in response to Manila's recent outreach in the energy sector. In an April 21 commentary, the People's Daily criticized the Philippines for provoking issues tied to China's core interests and urged it to stop such actions if it wants better relations. The commentary also condemned Manila's moves in the South China Sea and the US‑Philippine "Balikatan" exercises.

On April 21, the JMSDF confirmed one Russian Steregushchiy class frigate (hull number 335), one Improved Kilo class submarine and one Balk class (Project 23470 class) seagoing tug sailing northeast in waters 50km south of Yonagunijima Island (Okinawa Prefecture). These vessels sailed northeast through waters between Yonagunijima Island and Iriomotejima Island (Okinawa Prefecture) and navigated to the East China Sea.

On April 22, the JMSDF confirmed two Russian Steregushchiy class frigate (hull number 333 and 343) and one Dubna class medium replenishment ship sailing northeast in waters 70km south of Yonagunijima Island (Okinawa Prefecture). These vessels sailed northeast through waters between Yonagunijima Island and Iriomotejima Island (Okinawa Prefecture) and navigated to the East China Sea.

On April 22, the JMSDF confirmed one Chinese Luyang III class destroyer (hull number 133) and one Chinese Jangkai II class frigate (hull number 577) sailing northwest in waters 80km south of Haterumajima Island (Okinawa Prefecture). These vessels sailed northeast through waters between Yonagunijima Island and Iriomotejima Island (both in Okinawa Prefecture) and navigated to the East China Sea.

The head of US Indo-Pacific Command told a Senate hearing on April 21 that more ships are needed in the region amid China's rapid naval buildup. He said the fleet lacks amphibious ships, destroyers, and attack submarines, and also called for more medium and large unmanned vessels.

On April 21, Taiwan's Coast Guard said four vessels from China's Coast Guard and one vessel from its Maritime Safety Administration entered waters around Kinmen, describing the incident as harassment under the guise of law enforcement and a "grey-zone operation." The four coast guard vessels entered restricted waters in two groups before departing about two hours later. During the response, a Maritime Safety Administration vessel also entered Kinmen's waters. The Coast Guard said it would continue to defend sovereignty and ensure maritime security with a firm and professional stance.

On April 21, Taiwan's coast guard minister visited Itu Aba Island in the contested Spratly Islands in the South China Sea for an exercise. It was the first time in seven years a minister had visited the island. Taiwan has control of the island, which is also claimed by China, Vietnam and the Philippines. The island has a runway and a new wharf but it is lightly defended compared to nearby Chinese-controlled islands. Chinese forces generally leave the island alone.

Taiwan President's overseas trip on April 22 was canceled after three Indian Ocean island countries along the route revoked flight permits, the first time a Taiwanese president has been forced to cancel an entire overseas trip for this reason. ICAO requires member states to provide FIR information, but the three countries effectively refused these air traffic control duties. A Taiwan official reportedly said China pressured them with threats of economic sanctions, including revoking debt relief, while China denies the claims but expressed appreciation.

If China's pressure is the cause of the revocation, it would set a precedent of the international aviation network being used for political intimidation, hindering freedom of overflight. Japan's Chief Cabinet Secretary said aviation safety is important and that aviation authorities must operate with transparency, and a Japanese official added that weaponizing air traffic for political purposes must not be tolerated. Japan has been monitoring the situation and examining whether it would affect freedom of overflight under international law.

On April 23, the JMSDF confirmed two Russian Steregushchiy class frigate (hull number 333 and 343) and one Dubna class medium replenishment ship sailing northeast in waters 130km southwest of Goto Islands (Nagasaki Prefecture). From April 23 to 24, these vessels sailed northeast through the Tsushima Strait and navigated to the Sea of Japan.

From April 20 to 24, the Vietnam Coast Guard and the China Coast Guard conducted their first joint patrol of 2026 near the Gulf of Tonkin delimitation line, holding talks, coordinating action plans, and organizing professional legal exchanges. A Vietnamese official noted that maritime law enforcement cooperation remained effective, citing successful joint patrols and anti-crime operations in 2025. Both sides agreed to further expand cooperation in joint patrols, maritime law enforcement, search and rescue, and support for fishermen.

On April 27, two China Coast Guard vessels entered Japan's territorial waters off the Senkaku Islands in the East China Sea. Their hull numbers are 2302 and 2308 (Source: the JCG). According to the JCG, as the Chinese vessels tried to approach a Japanese fishing boat operating in the waters, the JCG patrol ships safeguarded the fishing boat and urged the Chinese vessels to leave the area. It was the first intrusion into the Japanese waters around the Senkaku chain by Chinese government vessels since April 14.

Note: The hull numbers reported above are taken from a JCG press release.

On April 27, the JMSDF confirmed one Chinese Luyang III class destroyer (hull number 120) and one Chinese Fuchi class replenishment ship (hull number 903) sailing southwest in waters 80km northeast of Tsushima Island (Nagasaki Prefecture). These vessels sailed southwest through the Tsushima Strait and navigated to the East China Sea.

On April 28, State Minister for Foreign Affairs of Japan attended the Security Council High-Level Open Debate on "The Safety and Protection of Waterways in the Maritime Domain," and delivered a statement on behalf of the Government of Japan.

She stated that the seas and oceans allow us to live and prosper and that the safety of passage must be upheld under the 1982 United Nations Convention on the Law of the Sea. She expressed concern about the situation in the East China Sea and the South China Sea, and reiterated Japan's opposition to any unilateral attempts to change the status quo by force or coercion, including obstruction of navigation and overflight.

She also noted Japan's promotion of a "Free and Open Indo-Pacific" over the past decade and its cooperation with the UN system in capacity-building for maritime nations. She concluded that Japan will continue working with the United Nations and member states to maintain a free and open maritime order based on the rule of law and ensure maritime safety and stability.

On April 28, Japan-Australia Foreign Ministers' Meeting was held in Tokyo.

They agreed to strengthen bilateral cooperation across a wide range of areas, including security, and to work together to advance a "Free and Open Indo-Pacific." They also discussed the Indo-Pacific situation and reaffirmed their commitment to close communication and cooperation on various issues.

On April 28, Japan's Defense Minister received a courtesy call from the Commander of U.S. Pacific Air Forces. They discussed bilateral defense cooperation, particularly in the Indo-Pacific region, and reaffirmed the robust Alliance, underpinned by close communication at all levels.

On April 28, two China Coast Guard vessels that had entered Japan's territorial waters off the Senkaku Islands in Okinawa Prefecture the previous day left the waters after sailing within them for more than 24 hours.

On April 29, the JCG reported that a Chinese oceanographic research vessel left Japan's EEZ off Ishigakijima Island in Okinawa Prefecture after operating without permission for about two weeks. On April 15, the JCG confirmed the vessel had extended what appeared to be a wire into the water and continued its activities despite a call from a JCG patrol ship to stop.

On April 29, the JCG confirmed that the Chinese oceanographic research vessel Xiangyanghong 22 had extended what appeared to be a pipe into the water within Japan's EEZ, about 63 km west-northwest of Uotsuri Island in the Senkaku Islands. The JCG requested that the activity stop, stating that surveys without consent are not permitted.