The Philippines has accused Chinese vessels of carrying out "dangerous maneuvers" in a disputed area of the South China Sea in the latest maritime flare-up between the two neighbors.
The Philippine coast guard said in a statement Friday it had been carrying out a routine rotation and resupply mission near Ayungin Shoal, known in China as Ren'ai Reef, when its vessels were approached by eight Chinese boats.
It claimed the Chinese boats "jeopardized" the safety of the crew members aboard the Philippine vessels, but did not detail how. It claimed the incident had involved four Chinese coast guard vessels and four Chinese "maritime militia" boats.
The incident comes just weeks after the Philippines accused Chinese coast guard ships of firing water cannons at its vessels as they tried to resupply troops stationed on the same shoal in the Spratly Islands chain, known in China as the Nansha Islands.
Western marine security experts believe Beijing controls a maritime militia hundreds of vessels strong that acts as an unofficial -- and officially deniable -- force to push its territorial claims both in the South China Sea and beyond.
The Philippines claims the militia has been involved in both of the most recent incidents at Ayungin Shoal, which is also known as Second Thomas Shoal.
China has never acknowledged that such a militia exists.
Following the most recent incident the Philippine coast guard said it had reached out to its Chinese counterpart and urged them to "immediately cease any illegal activities within the maritime zones of the Philippines."
Beijing claims "indisputable sovereignty" over almost all of the 1.3 million square mile South China Sea, as well as most of the islands within it. That includes the Spratlys, an archipelago consisting of 100 small islands and reefs also claimed in full or part by the Philippines, Malaysia, Brunei and Taiwan.
Manila however calls part of the area the West Philippine Sea. In 1999 it intentionally grounded a navy transport ship, the BRP Sierra Madre, on Second Thomas Shoal, manned by Filipino marines, to enforce the country's claim to the area.
In response to the latest confrontation, the Chinese coast guard issued a statement on Friday, accusing the Philippines of unauthorized entry into the area.
"Two Philippine supply ships and two (Philippine) coast guard ships entered the waters adjacent to Ren'ai Reef in China's Nansha Islands without permission from the Chinese government," the statement read.
"China has indisputable sovereignty over the Nansha Islands, including Ren'ai Reef, and its adjacent waters, and firmly opposes the Philippines' illegal transportation of illegal building materials to warships stationed on the beach illegally."
Manila's territorial claims are backed by the international Permanent Court of Arbitration in the Hague, which ruled in 2016 that China has no legal basis to claim historic rights to the bulk of the South China Sea.
Beijing has ignored the ruling and insists that the Philippines had promised to remove the vessel. Philippine President Ferdinand Marcos Jr. has said his government has never promised such a move.