By AFP and Liz Lagniton | 2026-05-11

MANILA -- The Philippine Coast Guard said on May 7 it deployed aircraft to issue radio warnings to a Chinese research ship operating near a disputed reef in the Spratly Islands. Manila is accusing Beijing of conducting unauthorized scientific activity inside the country's Exclusive Economic Zone (EEZ).

The Chinese vessel Xiang Yang Hong 33, capable of supporting submersible craft, was detected near Iroquois Reef at the southern end of Reed Bank, an area believed to contain significant natural gas and oil reserves.

Philippine authorities said the ship was deploying a service boat toward the reef during the operation, "confirming ongoing unauthorized marine scientific research operations."

Swarming vessels

During the patrol flight, the coast guard spotted 41 suspected Chinese "maritime militia vessels" anchored near Iroquois Reef and Philippine-held Thitu Island, home to about 400 residents and a newly established coast guard station.

"The presence of the research vessel and the large-scale swarming by Chinese Maritime Militia vessels represent a serious infringement on Philippine sovereign rights and maritime jurisdiction," the Philippine Coast Guard said in a statement.

"We will continue to challenge any illegal activities that undermine our sovereignty and sovereign rights," Philippine Coast Guard Commandant Admiral Ronnie Gil Gavan said, according to Reuters.

The Xiang Yang Hong 33 has been monitored near several Philippine-claimed features in recent weeks, including Sabina Shoal and Second Thomas Shoal, both recurring flashpoints between Chinese and Philippine forces.

Maritime pressure

The latest encounter followed another Philippine operation on May 3, when authorities deployed aircraft and vessels under orders from President Ferdinand Marcos Jr. to challenge four Chinese research ships detected across multiple areas within Manila's EEZ.

Philippine monitoring identified the vessels as Xiang Yang Hong 33, Shi Yan 1, Jia Geng and Zhuhaiyun, which Manila described as specialized research ships capable of deep-sea mapping, acoustic surveys and unmanned system deployment.

"We will not tolerate any illegal marine scientific research conducted without our government's consent," Gavan said on May 3.

Competing claims

Manila said the Chinese operations violated Philippine sovereign rights and the United Nations Convention on the Law of the Sea, which requires coastal-state approval for scientific research conducted within an EEZ.

Beijing, which claims most of the South China Sea despite a 2016 international tribunal's rejection of its case, defended the operations as lawful and said the islands and reefs involved were Chinese territory.

Meanwhile, civilian activists from the Atin Ito ("This Is Ours") coalition May 3 conducted a symbolic flag-planting mission at Sandy Cay, another move aimed at reinforcing Manila's presence in the disputed waters.

Akbayan Rep. Dadah Kiram Ismula, who joined the mission, said that the Filipinos spotted Chinese coast guard and naval ships nearby during the operation.

"There was a Chinese vessel that tried to pursue us," Ismula told reporters, according to the Philippine Star.

The Armed Forces of the Philippines later described the operation as "a powerful assertion of our sovereign rights and a demonstration of active citizenship in the face of external challenges."

The Philippine military separately reported monitoring 62 Chinese naval and coast guard vessels across key areas of the West Philippine Sea in April, including Scarborough Shoal, Second Thomas Shoal, Sabina Shoal and Thitu Island.