The Philippines has accused China's coast guard of water-cannoning one of its supply boats in the South China Sea.

The Armed Forces of the Philippines said two chartered private vessels were on a routine troop rotation and resupply mission accompanied by two Philippine Coast Guard vessels.

The Philippine military said one of the boats was "blocked and water cannoned" by a Chinese vessel in waters near the Spratly Islands on Saturday. It said this prevented the other boat from unloading its supplies.

The military denounced the actions in a statement, calling it "wanton disregard of the safety of the people on board" and a "violation of international law."

It said it "strongly condemns and expresses grave concern over the China Coast Guard's excessive and unlawful actions."

But a spokesperson for the China Coast Guard asserted in a statement on Sunday that four Philippine vessels had "illegally intruded into the waters."

The statement said China's coast guard had implemented necessary controls in accordance with the law. It also urged the Philippines to immediately stop activities that infringe China's rights in the waters.

It said China has "indisputable" sovereignty over the islands and their adjacent waters. It also said the coast guard will continue to "carry out rights protection and law enforcement activities in the waters under China's jurisdiction in accordance with law."