The Philippine Coast Guard on Sunday reported the detection of unauthorized marine scientific research activities near Pag-asa Island in the West Philippine Sea over the weekend of 16 to 17 May.

In a statement released through the Philippine Information Agency, the PCG said it monitored the China-flagged research vessel Xiang Yang Hong 33 on 16 May.

Authorities described the vessel as an advanced oceanographic survey ship capable of supporting submersible craft and conducting marine ecological surveys, bathymetric mapping, and deep-sea data collection.

The research vessel was reportedly escorted by Chinese Coast Guard ships CCG 5101 and CCG 5309.

The PCG also noted what it described as illegal activities conducted by Chinese personnel during the intrusion.

“Chinese personnel were observed landing and conducting illegal activities on Cay-2 before proceeding to Cay-3,” the PCG said.

According to the Coast Guard, the Xiang Yang Hong 33 had been conducting suspicious activities since entering the West Philippine Sea on 18 April.

“Since its entry into the Philippine exclusive economic zone almost a month ago, the vessel has been systematically conducting illegal MSR activities across multiple features in Philippine waters,” the PCG added.

In response, PCG Commandant Admiral Ronnie Gil Gavan directed the deployment of PCG Islander 4177 to conduct a maritime domain awareness flight over the Kalayaan Island Group on 17 May.

The flight reportedly monitored unauthorized operations near Sandy Cay 2 and confirmed the presence of the Chinese research vessel and its escort ships conducting marine scientific research without Philippine government authorization.

The aerial patrol also documented 20 Chinese Maritime Militia Vessels scattered around the waters near Sandy Cay 3 and 4.

The PCG stressed that the unauthorized entry and marine research activities violated Philippine sovereign rights and the United Nations Convention on the Law of the Sea.

According to the statement, PCG aircraft repeatedly issued radio challenges demanding that the Chinese vessels stop their activities.

“The PCG will continue to monitor the area and take all necessary measures to protect Philippine sovereign rights and jurisdiction,” the agency said.

Gavan also vowed that the PCG would continue preventing unauthorized foreign activities near Pag-asa Island.

“We will not allow any unauthorized foreign research or incursions into our territorial sea in Pag-asa Island in accordance with the directive of President Ferdinand Marcos Jr.,” Gavan said.