A China Coast Guard ship (L) releasing water cannon on a Philippine Coast Guard ship near Second Thomas Shoal during a re-supply mission on August 5. AFP
The latest incident happened Saturday as the Philippine Coast Guard escorted vessels carrying food, water, fuel and other supplies for Filipino military personnel stationed at Second Thomas Shoal in the Spratly Islands.
In a statement, the US State Department condemned the Chinese actions, saying they were carried out by the coast guard and "maritime militia", and that they directly threatened regional peace and stability.
China claims almost all of the sea, through which trillions of dollars in trade passes annually, with competing claims from Brunei, Malaysia, the Philippines, Taiwan and Vietnam.
Its coast guard and navy vessels routinely block or shadow Philippine ships patrolling the contested waters, Manila says.
Saturday's incident was the first time since November 2021 that the Chinese coast guard had used water cannon against a Philippine resupply mission to Second Thomas Shoal.
"The Philippine Coast Guard (PCG) strongly condemns the China Coast Guard's (CCG) dangerous manoeuvres and illegal use of water cannons against the PCG vessels," the Philippine Coast Guard said in a statement.
"Such actions by the CCG not only disregarded the safety of the PCG crew and the supply boats but also violated international law."
The Armed Forces of the Philippines said the Chinese coast guard had "blocked and water cannoned" one of its chartered resupply vessels.
Due to the "excessive and offensive" actions, a second chartered vessel was unable to unload its cargo for the routine troop rotation and resupply operation, military spokesman Colonel Medel Aguilar said in a statement.
"We call on the China Coast Guard and the Central Military Commission to act with prudence and be responsible in their actions to prevent miscalculations and accidents that will endanger peoples' lives," Aguilar said.
The Chinese embassy in Manila did not immediately respond to a request for comment.
Manila and Beijing have a long history of maritime disputes over the South China Sea, particularly in the waters around Second Thomas Shoal
After China occupied Mischief Reef in the mid-1990s, the Philippines ran a derelict navy vessel aground on the nearby shoal to assert Manila's territorial claims in the waters.
Members of the Philippine marines are based there.
A similar incident happened in June during another regular resupply operation.
As they neared the shoal, the two Philippine coast guard boats assigned as escorts for that navy mission were approached by two Chinese coast guard vessels.
One of the Chinese boats came within about 100 yards (90 metres) of the BRP Malabrigo's bow, forcing its commanding officer to slow down to avoid a collision, the coast guard said previously.
Another incident happened in April when a Chinese coast guard ship cut off the Philippine patrol vessel Malapascua as it carried journalists near Second Thomas Shoal.
An AFP team was on another coast guard vessel and witnessed the near-collision.
In that incident, the Malapascua's commanding officer Rodel Hernandez said the Chinese ship came within 45 metres of his boat and only his quick actions avoided the steel-hulled vessels crashing into each other.