Manila accused Chinese ships of firing water cannons and making “dangerous maneuvers” toward Philippine vessels resupplying a remote military outpost on Friday, in the latest of a string of incidents between the two countries in the disputed South China Sea.

Philippine authorities said a Chinese coast guard vessel had fired water cannon against its vessel M/L Kalayaan in “an illegal though unsuccessful attempt to force [it] to alter course,” as it took part in a routine resupply mission to troops stationed on the BRP Sierra Madre in the Second Thomas Shoal.

The Philippines also claimed that vessels belonging to a Chinese maritime militia were involved in the harassment and that two Philippine boats were subjected to “reckless” and “dangerous” harassment by inflatable boats belonging to the Chinese coast guard.

The BRP Sierra Madre is a former US Navy ship the Philippines grounded in 1999 at the Second Thomas Shoal – known as Ayungin Shoal to Manila and Ren’ai Reef to Beijing – to enforce its claim to the area.

That claim is hotly disputed by China and the two countries have been involved in increasingly frequent run-ins in the highly contested waterway.

A spokesperson for China’s coast guard, Gan Yu, said in a statement that two small transport vessels and three marine police vessels from the Philippines “entered the waters adjacent to Ren’ai Reef in China’s Nansha Islands without the permission of the Chinese government.”

The statement claimed China has “indisputable sovereignty over the Nansha Islands and their adjacent waters, including Ren’ai Reef,” adding the “actions of the Philippine side infringe on China’s territorial sovereignty” and urging Manila to “immediately stop its infringing actions.”

The latest incident near Second Thomas Shoal in the Spratly Islands comes nearly three weeks after Beijing and Manila blamed each other for two collisions near the same area.

In its statement following the latest incident, the Philippines said it condemned “once again, China’s latest unprovoked acts of coercion and dangerous maneuvers against a legitimate and routine Philippine rotation and resupply mission.”

China’s actions had not only “put the lives of our people at risk,” but had “put into question and significant doubt the sincerity of its calls for peaceful dialogue,” it added.

Filipino troops stationed on the BRP Sierra Madre live under spartan conditions on the mostly rusted wreckage of the World War II era ship and rely on the regular delivery of supplies.

Despite the run-in Friday, the Philippine government said the resupply mission was completed.

Beijing claims “indisputable sovereignty” over almost all of the South China Sea, and most of the islands and sandbars within it, including many features that are hundreds of miles from mainland China, in defiance of an international court ruling in 2016 that sided with the Philippines.

The Philippine Embassy in Beijing has protested to the Chinese Foreign Ministry over the latest incident.

The South China Sea is widely seen as a potential flashpoint for global conflict. The recent confrontations between Manila and Beijing have raised concerns among Western observers that the disputes could potentially develop into an international incident if China, a global power, decides to act more forcefully against the Philippines, a US treaty ally.