The Philippine government has called for China to exercise restraint in the disputed South China Sea. The remark came one day after Chinese Coast Guard ships fired water cannons at a Philippine military supply vessel, injuring four crew members.

Manila says it was the most serious incident in a recent series of clashes, and is urging China to resolve the issue through diplomacy without further heightening tensions.

The Philippines' South China Sea task force said at a news conference on Wednesday that the water cannon shattered windows in the vessel, injuring the crew.

It said that China deployed five Coast Guard vessels and 18 large fishing boats believed to be carrying maritime militia, with three naval ships behind them.

Jonathan Malaya, Assistant Director General of the Philippine National Security Council said: "The Chinese Coast Guard conducted provocative, unilateral, illegal and unprofessional acts. We hold the Chinese coastguard responsible for their actions."

Chinese Coast Guard ships on Tuesday also collided with Philippine vessels on a routine resupply mission to a military outpost on Second Thomas Shoal.

The Philippine Foreign Ministry summoned China's deputy chief of mission in Manila to convey its protest.

Chinese Foreign Ministry Spokesperson Mao Ning said: "The Philippines broke its promise and violated China's sovereignty and maritime interests. China took necessary measures in accordance with the law and acted in a restrained manner."

She added that the responsibility lies entirely with the Philippines.