The Philippine Navy monitored 49 Chinese vessels in the West Philippine Sea from 15 March to 22 March, up from 30 recorded in the previous monitoring period, a Navy official said Tuesday.

Rear Admiral Roy Vincent Trinidad, Philippine Navy spokesperson for the West Philippine Sea, said the vessels were sighted in several key areas, with the largest concentration monitored near Bajo de Masinloc.

Of the 49 vessels, 28 were seen at Bajo de Masinloc, including nine People’s Liberation Army Navy ships and 19 China Coast Guard vessels. Eight vessels were monitored at Ayungin Shoal, consisting of three Chinese navy ships and five China Coast Guard vessels. Five were spotted at Escoda Shoal, including three navy ships and two coast guard vessels, while another eight were seen near Pag-asa Island, composed of one navy ship and seven coast guard vessels.

The latest tally marked an increase from the 30 Chinese vessels monitored in West Philippine Sea features from 1 March to 8 March, based on previous military monitoring.

Meanwhile, Philippine Coast Guard spokesperson for the West Philippine Sea Rear Admiral Jay Tarriela said the agency had, for the first time, documented the China Coast Guard announcing over radio its intention to conduct a so-called “clearing operation” near Bajo de Masinloc, also known internationally as Scarborough Shoal.

Tarriela said the warning was intercepted by the Philippine side during a patrol flight. He said the move appeared intended to intimidate Filipino fishermen operating in the area, which has long been a traditional fishing ground for local fishers.

The West Philippine Sea refers to the maritime areas on the western side of the Philippine archipelago, including the Luzon Sea, waters around and adjacent to the Kalayaan Island Group, and Bajo de Masinloc. In 2016, an arbitral tribunal in The Hague ruled that China’s sweeping claims in the South China Sea had no legal basis under international law.