Philippine coast guard confronts Chinese deep-sea research ship as PLA warships sail nearby

The Philippine Coast Guard (PCG) has sent an aircraft and patrol vessels to challenge a Chinese deep-sea research ship that it says is surveying the seabed without permission near Hubo Reef in the Spratly Islands, where two Chinese navy vessels and two China Coast Guard ships were also tracked. The PCG spokesman for the West Philippine Sea, Jay Tarriela, announced the deployment on Sunday, 11 October 2026.

Using its Dark Vessel Detection system and ship-tracking data, the PCG said the Tan Suo Yi Hao left waters near Sanya on Hainan island on 2 October, sailed down the western side of the South China Sea and entered the Philippine exclusive economic zone (EEZ) on the evening of 9 October. By the next morning it was lying about 12 nautical miles northwest of Katimugan Bank, broadcasting that it was carrying out diving operations with restricted manoeuvrability and asking other ships to stay two nautical miles clear.

The ship also gave 17 October as its estimated arrival date, which the PCG read as a sign that it intends to stay in the area for at least another week. It briefly stopped transmitting its position before reappearing, and early on Sunday afternoon it was about 5.6 nautical miles west-northwest of Hubo Reef and roughly 117 nautical miles northwest of Rizal, Palawan, still declaring diving operations.

A PCG Islander patrol aircraft flying from Antonio Bautista Air Base in Puerto Princesa found the vessel at 8:13 that morning, moving slowly east. The crew saw no submersible, equipment or lines in the water at the time, and the ship did not answer repeated radio challenges.

On the same flight the aircrew spotted China Coast Guard ship 5306 about 6.8 nautical miles south of Hubo Reef and a second coast guard ship 12.7 nautical miles to the southwest. Two People's Liberation Army Navy vessels were operating nearby, one about 22.8 nautical miles northeast of Escoda Shoal and the other 11.3 nautical miles south-southeast of Katimugan Bank. PCG Commandant Admiral Ronnie Gil Gavan then ordered coast guard vessels to the area to confront the research ship directly and disrupt its work.

According to the PCG, the Tan Suo Yi Hao is run by the Chinese Academy of Sciences' Institute of Deep-sea Science and Engineering in Sanya and serves as the mothership for China's crewed deep-sea submersibles, including the Fendouzhe. It carries deep-sea winches, sounding systems and sediment samplers, and the PCG said it is the first of the Chinese research ships it has recently tracked to openly declare diving inside the Philippine EEZ, as well as the one operating farthest south.

The Department of Foreign Affairs confirmed that China had not asked for consent for any research by the ship. The PCG said that under the UN Convention on the Law of the Sea, marine research in a coastal state's EEZ and continental shelf requires that state's permission, so any seabed survey, sampling or mapping by the vessel is illegal.

Gavan said China was using fishing boats and research ships in several parts of Philippine waters to spread the coast guard thin, strain its logistics and pressure Manila into accepting Beijing's claims, and he pledged not to give up any territory. The PCG listed recent cases including the research ship Jia Hai Ke 7 off Batanes, a militia vessel and 22 small boats it drove from Kota Island on 9 October, and a survey ship that loitered off Scarborough Shoal for nearly a month.

Later on Sunday, Tarriela said a Chinese statement had not disputed the ship's position or the presence of the navy and coast guard vessels, only Manila's right to act. He argued that warships positioned around a research vessel were serving as escorts rather than routine patrols, and that seabed data has military as well as resource value.

The ship's declared stay until 17 October means the coast guard may need to keep vessels on station for days in an area where Chinese naval ships are already present, the kind of drawn-out commitment Gavan says Beijing is trying to impose.