Chinese warships, drones and a patrol plane gather at Scarborough Shoal around a Philippine frigate

At least nine Chinese military and coast guard assets were tracked near Scarborough Shoal, which Manila calls Bajo de Masinloc, on 16 October, the Philippine Navy said, noting a slight increase in the number of Chinese naval and coast guard ships after its frigate had reported three Chinese ships in the area a day earlier. According to ABS-CBN News, the group was made up of four People's Liberation Army Navy warships, one of them a supply ship, two China Coast Guard vessels, two unmanned aerial vehicles and one maritime patrol aircraft.

Lieutenant Commander Bryan Magura, executive officer of the guided-missile frigate BRP Miguel Malvar, told reporters he believed the Chinese units had been alarmed by the Philippine Navy's presence and had consolidated around the area where his ship was operating. He said the crew had not seen the Chinese ships try to obstruct the frigate, and that they had only answered its radio challenges with their own routine challenges.

The frigate worked its way around the shoal during the day, moving from the southern sector to the west and north before crossing to the eastern side, the broadcaster reported. Philippine aircraft also flew over the feature. A Cessna from the Bureau of Fisheries and Aquatic Resources patrolled at about 8 am, and a Philippine Air Force fixed-wing aircraft followed at around 9 am, with both issuing radio challenges to every ship near the shoal.

The day before, the navy had called its patrol and maritime domain awareness flight around the shoal generally successful. Captain Paul Michael Hechanova, the frigate's commanding officer, said on 15 October that there had been no untoward incident or aggressive act from the Chinese ships then present, which were a Jiangkai-class frigate with bow number 544, a second navy vessel and a coast guard ship, DZRH reported. A Chinese naval helicopter shadowed the Philippine helicopter during that flight, and its pilot reported possible maritime militia boats and a suspected research ship about 500 yards from the shoal, a sighting the navy said it was still verifying.

The Miguel Malvar's patrol came straight after the 16th bilateral maritime cooperative activity between the Philippine armed forces and the US Navy, held on 14 October inside the Philippine exclusive economic zone. US 7th Fleet said the frigate sailed with the Philippine Coast Guard patrol vessel BRP Melchora Aquino and the Avenger-class mine countermeasures ship USS Warrior, supported by Philippine aircraft.

The US fleet said the exercise concentrated on tactical interoperability, maritime domain awareness and a group sail to build proficiency at sea, and that it was carried out with due regard for the navigational rights of all nations. The Philippine military said the one-day activity also included passing honours and a photo exercise and was meant to improve coordination between the two forces, the Daily Tribune reported.

Scarborough Shoal lies inside the Philippines' 200-nautical-mile exclusive economic zone and is a traditional fishing ground for Filipino fishers, and the 2016 arbitral award on the South China Sea recognised the traditional fishing rights of both Filipino and Chinese fishers there. Chinese navy and coast guard ships were present around the shoal on both days of the Philippine patrol.

The Philippine accounts did not say how long the larger Chinese group stayed near the shoal, whether it had thinned out by the evening, or how close any of the warships came to the Miguel Malvar during the day.