MANILA — The Philippines accused Chinese maritime officials on Oct 4 of carrying out an "unjustified assault" on Vietnamese fishermen in the contested waters of the South China Sea, adding its voice to a fraught dispute over the confrontation.

Vietnam said this week that Chinese law enforcement officers had beaten 10 fishermen and seized their gear while they were working on Sep 29 near the Chinese-controlled Paracel Islands, which Hanoi also claims and calls Hoang Sa.

China, which claims most of the busy waterway, said on Oct 1 the fishermen had been there illegally and that it had taken steps to stop them. It did not respond immediately to the Philippine statement.

Other recent run-ins between China and the Philippines, a US treaty ally, have made the highly strategic South China Sea a potential flashpoint between Washington and Beijing.

Philippine National Security Adviser Eduardo Ano said on Sep 27 his country stood with Vietnam in denouncing the "egregious act" on Sept 29.

"Such use of force against civilians blatantly violates international law ... and breaches basic human decency," he added in his statement.

The Philippines and Vietnam also have overlapping claims on islands in the South China Sea, but both agreed in August to work more closely together and resolve disagreements peacefully.

Their coastguards held their first joint exercises in August.

Encounters have become more frequent in the past year as Beijing presses its claims and Manila refuses to halt fishing and resupply activities for Philippine military personnel at two contested shoals.

China uses a so-called nine-dash line that takes in about 90 per cent of the South China Sea to assert its claim to sovereignty over nearly all of the strategic waterway, and has deployed hundreds of coast guard vessels in patrols against rival claimants.

China regularly says its coast guard is acting professionally and lawfully to protect its territory from trespassers.

The US has a mutual defence treaty with the Philippines and has repeatedly made clear it would protect its ally if Manila's coast guard or armed forces came under attack anywhere in the South China Sea.

The Philippine foreign ministry also weighed in on Oct 4, saying it was aware of a "serious incident" between Vietnamese fishermen and Chinese maritime authorities and "emphasised the need for actors to exercise genuine self-restraint".

ALSO READ: Philippines says China's South China Sea moves 'aggressive, unprofessional and illegal'

Source: Reuters