PCG challenges China research ship off Cagayan province

The Philippine Coast Guard (PCG) has monitored the presence of a Chinese research vessel off the coast of Cagayan province in northern Luzon, prompting it to challenge the ship's presence within the country's exclusive economic zone.

In a social media post late Tuesday night, PCG spokesperson for the West Philippine Sea (WPS) Jay Tarriela said Chinese Research Vessel (CRV) Tan Suo Er Hao was spotted about 19 nautical miles off the Cagayan coast.

PCG Commandant Admiral Ronnie Gil Gavan then ordered the deployment of a PCG Islander aircraft on Tuesday morning to conduct a Maritime Domain Awareness (MDA) flight to challenge the ship's presence.

According to the PCG, the operation also sought to verify if the vessel was conducting marine scientific research without prior clearance from the Philippine government.

Tarriela said such actions are in potential violation of the Philippine Maritime Zones Act and the United Nations Convention on the Law of the Sea (UNCLOS).

PCG Challenges Chinese Research Vessel Operating Near Cagayan Waters

The Philippine Coast Guard (PCG), utilizing the Canada’s Dark Vessel Detection program, detected the Chinese Research Vessel (CRV) Tan Suo Er Hao approaching within approximately 19 nautical miles off the coast… pic.twitter.com/8xUl9aZla6

— Jay Tarriela (@jaytaryela) December 30, 2025

The ship was spotted through Canada's Dark Vessel Detection technology.

During the MDA flight, the PCG aircraft sighted the Tan Suo Er Hao heading eastward 55.78 nautical miles east of Santa Ana, Cagayan. 

Monitoring data showed that the vessel departed from Hainan province in China earlier this month and sailed through the western portion of the Philippine EEZ.

The PCG described the Tan Suo Er Hao as an 87.25-meter advanced deep-sea scientific research vessel operated by the Institute of Deep-sea Science and Engineering under the Chinese Academy of Sciences. It is designed to serve as a mothership, the PCG said, for manned and unmanned deep-sea submersibles and to support a wide range of deep-sea operations.

"The PCG pilot issued multiple radio challenges to the vessel, inquiring about its intentions and reminding it of the requirement for prior consent for marine scientific research in Philippine waters. The CRV Tan Suo Er Hao did not respond to any of the radio calls," Tarriela said.

The Chinese Embassy in Manila, however, insisted that the ship "was conducting normal navigation" as Beijing does not recognize the Philippine Maritime Zones Act.

It added that China disagrees with the Philippine Archipelagic Sea Lanes Act's designation of the Balintang Strait as the only strait for international passage in northern Philippines.

"China enjoys the right of passage through the archipelago maritime route in accordance with international law, including UNCLOS," the Chinese embassy said. — VDV, GMA Integrated News