The BRP Diego Silang issued four radio challenges to Chinese vessels during a maritime patrol near Bajo de Masinloc in the West Philippine Sea, according to Philippine Coast Guard spokesperson for the West Philippine Sea, Rear Admiral Jay Tarriela.

Tarriela said a Bureau of Fisheries and Aquatic Resources (BFAR) maritime domain awareness flight on Monday documented the Chinese research vessel Yue Zhan Yu Ke 6 towing a floating platform through the southeast entrance of the shoal.

The flight also observed a service boat repositioning the floating structure after the research vessel had re-entered the area.

Aside from a People’s Liberation Army Navy frigate bearing bow number 555, a China Coast Guard vessel was also monitored in the vicinity during the patrol.

Tarriela said that when the BFAR aircraft departed Monday afternoon, the floating platform remained at the stern of Yue Zhan Yu Ke 6, while vessel Xia Yu Zhi 20028 was positioned alongside it.

China claims nearly the entire South China Sea, including Masinloc (Scarborough Shoal), through its so-called nine-dash line.

The Philippines asserts sovereign rights over the area under the United Nations Convention on the Law of the Sea.

In 2016, an arbitral tribunal ruled that China’s sweeping claims had no legal basis under international law.

The Philippine Coast Guard earlier reported that the Chinese floating structure had been moved from the entrance of Bajo de Masinloc to inside the shoal.