The Philippines' military chief on Monday accused China's coast guard of firing water cannon at Filipino fishermen for the first time to drive them away from a disputed sea shoal.

General Emmanuel Bautista said Chinese vessels fired cannon on January 27 near Scarborough Shoal -- the subject of a bitter territorial row in the strategically important South China Sea.

"The Chinese coast guard tried to drive away Filipino fishing vessels to the extent of using water cannon," Bautista told a forum of the Foreign Correspondents Association of the Philippines.

He did not say if anyone was hurt and added that China continues to maintain an armed coast guard and other vessels at the shoal.

China's foreign ministry spokeswoman Hua Chunying did not directly address the allegation when asked about it on Monday.

"I would like to re-emphasise that China has indisputable sovereignty over relevant waters and China's maritime surveillance fleet are carrying out routine patrols in relevant waters," she told reporters in Beijing.

Scarborough Shoal lies 220 kilometres (135 miles) off the main Philippine island of Luzon. It is about 650 kilometres from Hainan island, the nearest major Chinese land mass.

In April 2012, the Philippines and China had a tense standoff which ended with the former retreating from the shoal -- a rich fishing area.

Manila claims Beijing has effectively gained control of the shoal, while China says the shoal is part of its historical claim to most of the South China Sea including waters near the coasts of its neighbours.

The Philippines, along with Brunei, Malaysia, Taiwan and Vietnam also have competing claims to parts of the sea, and the rivalries have been a source of tension for decades.

The South China Sea is one of the world's most important waterways as it is home to vital shipping lanes and is believed to sit atop lucrative deposits of natural resources.

Philippines takes China to court

Last year, Manila asked a United Nations arbitration tribunal to rule on the validity of China's claim to most of the sea, but Beijing has refused to be part of the process.

"We continue to give primacy to its (the dispute's) peaceful resolution principally through international arbitration," Bautista said.

"All our actions are in support to that. We remain hopeful that the issue can be resolved peacefully and result in peace and stability in the region."

He added that "our resolve to perform our mandate as protectors of the people and the state and of our national territory" had not been weakened.

"We will continue to perform that mandate with whatever we've got," he said, adding that the country was in the first phase of modernising its poorly-equipped armed forces.

The Philippines has closely looked to its traditional ally, the United States, to counter what it sees as an increasingly aggressive China.

Manila has since 2011 acquired two US warships to patrol its territorial waters, while holding joint war games with the United States close to disputed areas.

It is currently negotiating a deal for increased US troop presence in the country, which is largely expected to be signed in time for President Barack Obama's visit to the Philippines in April.

The deal would expand the rotational number of American soldiers in the Philippines, as well as allow the US military to preposition equipment that could be used in quickly responding to disasters, officials said.

The talks had hit a snag late last year when the Philippines demanded "equal access" to US facilities that may be built in the country.