Malacañang on Thursday assured the public that the Philippine Coast Guard (PCG) and the National Task Force for the West Philippine Sea (NTF-WPS) continue to monitor the situation in the West Philippine Sea (WPS) following reports that two Chinese military hydrographic survey vessels entered Philippine maritime areas on 11 September.

The reported presence of the vessels adds to China's continuing and increasingly assertive activities in the disputed waters.

Sources identified the vessels as Hai Yang 23 Hao (Qian Xuesen 873) and Hai Yang 24 Hao (Deng Jiaxian 874), both Type 636A hydrographic survey ships operated by the People's Liberation Army Navy and capable of collecting detailed seabed and marine environmental data for both civilian and military purposes.

Hai Yang 23 was detected about 1.15 nautical miles south of Galoc Island, Palawan, while Hai Yang 24 was reportedly about 64.28 nautical miles west-northwest of Panatag Shoal, near submarine cable infrastructure.

Hydrographic surveys can reveal detailed information on water depths and seabed conditions.

Under Republic Act No. 12065, foreign vessels exercising archipelagic sea-lanes passage are prohibited from conducting hydrographic or oceanographic surveys without prior Philippine authorization. The United Nations Convention on the Law of the Sea (UNCLOS) likewise recognizes Philippine jurisdiction over marine scientific research within its exclusive economic zone.

“The verification of the report is ongoing at may mga barko ang PCG na nagbabantay doon sa area. More details to follow,” Presidential Communications Office Undersecretary and Palace Press Officer Claire Castro said during a media briefing.“On the intentions of China in doing so, we cannot answer because the PCG is still verifying such report. With regard to the messages of Defense Secretary Gibo Teodoro against China, they were based on the law and our rights. Isa po siyang opisyal na dapat ipaglaban ang interes at karapatan ng ating mga kababayan at ng ating bansa sa nasabing maritime rights,” Castro added.

Calls for closer scrutiny

West Philippine Sea rights advocate Dr. Jose Antonio Goitia said the vessels' reported proximity to submarine cables makes the sightings more significant.

Undersea cable networks carry about 99 percent of global internet traffic and connect the Philippines with the rest of the world, making nearby military survey activity worthy of closer scrutiny, he said.

“These are not ordinary research vessels. They are military survey ships capable of collecting detailed information about our maritime environment. When they operate in strategically sensitive areas, the Philippines has every reason to ask what they are mapping and why.”

Philippine authorities recently reported the presence of 48 Chinese Coast Guard and People's Liberation Army Navy vessels across four key West Philippine Sea features from 8 to 14 September, underscoring Beijing's sustained maritime presence in the area.

Goitia urged the government to remain vigilant.

“We should not be intimidated by foreign military vessels in our maritime domain. Track them, document their activities, and defend our rights. A sovereign nation must know what is happening in its own waters.”

He noted that while detailed seabed data have legitimate scientific uses, the same information can also support military operations, including naval navigation and submarine activities.

“Our seabed is part of our national security. Our undersea cables are part of our national infrastructure. We have every right to protect them and to know who is operating around them,” Goitia said.