The Chinese coast guard attacked Philippine vessels with water cannon blasts and rammed one of them, causing damage and endangering Filipino crew members off a disputed shoal in the South China Sea, officials said.

The Philippines and its treaty ally, the United States, condemned the latest confrontation near the Second Thomas Shoal, where two Philippine navy-operated supply boats and two Philippine coast guard escort ships to deliver food and other supplies to Filipino forces in a long-marooned navy ship that serves as a territorial outpost.

“We condemn, once again, China’s latest unprovoked acts of coercion and dangerous manoeuvres against a legitimate and routine Philippine rotation and resupply mission to Ayungin Shoal that has put the lives of our people at risk,” a Philippine government task force that deals with the territorial disputes said in a statement.

“The systematic and consistent manner in which the People’s Republic of China carries out these illegal and irresponsible actions puts into question and significant doubt the sincerity of its calls for peaceful dialogue,” it said. “We demand that China demonstrate that it is a responsible and trustworthy member of the international community.”

Philippines South China Sea
A Chinese coast guard ship rams the Philippine navy-operated supply boat Unaizah Mae 1 (Philippine Coast Guard via AP)

US Ambassador to Manila MaryKay Carlson said her country “stands with the Philippines and partners in vehemently condemning the PRC’s repeated illegal and dangerous actions against Philippine vessels”.

“(Chinese) aggression undermines regional stability in defiance of a free and open Indo-Pacific,” Ms Carlson added.

The Chinese coast guard said it had “implemented controls in accordance with laws and regulations” on Sunday against two Philippine coast guard vessels, including one official ship and one supply ship that were attempting to transport construction materials to the Second Thomas Shoal.

The statement gave no details about the measures taken but said the Philippines action “seriously infringed on China’s sovereignty”.

It also claimed a Philippine vessel ignored warnings and in violation of international navigation regulations made a sharp turn in an “unprofessional and dangerous manner” and intentionally collided with a Chinese coast guard ship, causing “scratching”.

“The responsibility lies entirely with the Philippine side,” the coast guard said.

China’s ships, which have surrounded the Philippine-occupied Second Thomas Shoal for years, have blocked Philippine coast guard and supply boats in a years-long effort to take control of the hotly disputed atoll claimed by both nations.

The hostilities, which have grown increasingly heated this year, have stoked fears of an armed conflict that could involve the United States, which has vowed to defend the Philippines, its treaty ally, if Filipino forces come under an armed attack.

The Chinese coast guard’s high-pressure water cannon blasts disabled and severely damaged the engines of the Philippine supply boat M/L Kalayaan, which had to be towed back to the western Philippine province of Palawan, Philippine officials said, adding the assault seriously endangered the lives of the crew.

One of two Philippine coast guard escort ships, the BRP Cabra, sustained damage to its mast due to the water cannon blast. Another supply boat was rammed by a Chinese coast guard ship but still managed to manoeuvre away and deliver supplies to Filipino marines at Second Thomas Shoal, they said.

Drone video footage and photographs issued by the Philippine coast guard show two Chinese coast guard ships separately blasting water cannons at close range at BRP Cabra and a smaller supply boat.

Philippines South China Sea
A Chinese coast guard ship, right, uses its water cannons on a Philippine Bureau of Fisheries and Aquatic Resources vessel as it approaches Scarborough Shoal in the disputed South China Sea (Philippine Coast Guard via AP)

In Saturday’s confrontation, the Chinese coast guard and accompanying ships also trained water cannons at three Philippine fisheries vessels to prevent them from approaching Scarborough Shoal in the disputed waters off the north-western Philippines.

That assault caused “significant damage” to the communication and navigation equipment of one of the three Philippine Bureau of Fisheries and Aquatic Resources vessel, Philippine officials said. The Philippines, the US and Japan condemned the Chinese action.

Philippine officials added that in addition to the use of water cannons on Saturday, suspected militia vessels accompanying Chinese coast guard ships used a long-range acoustic device that could impair hearing, causing “severe temporary discomfort and incapacitation to some Filipino crew”.

In other high seas clashes this year, Chinese coast guard ships used a military-grade laser that caused Filipino crewmen temporary blindness and engaged in dangerous blocking and shadowing manoeuvres that caused minor collisions, Philippines officials say.