Philippines soldiers used their "bare hands" to fight off Chinese coast guard personnel armed with swords, spears and knives in the disputed South China Sea, the country's top military commander has said.
General Romeo Brawner accused Chinese vessels of ramming Philippine boats, then boarding them and seizing weapons.
One Filipino soldier lost a thumb when his vessel was rammed, the general said. China denied its personnel were to blame, saying they had been "restrained".
There have been a string of dangerous encounters as the two sides seek to enforce their claims on disputed reefs and outcrops - this appears to be an escalation.
The skirmish happened as the Philippine navy and coast guard were delivering supplies to Filipino troops stationed in the Second Thomas Shoal.
Gen Brawner said soldiers reported seeing the Chinese coast guard armed with knives, spears and bolos, Filipino for sword. He said it's the first time Filipino troops had seen the Chinese using this type of weapon in the area.
"We saw in the video how the Chinese even threatened our personnel by pointing their knives at our personnel," Gen Brawner said.
Chinese personnel also seized a number of guns and destroyed items - including motors - and punctured inflatable vessels.
The incident, he added, amounted to "piracy".
"They have no right or legal authority to hijack our operations and destroy Philippine vessels operating within our exclusive economic zone," Gen Brawner told reporters.
But Beijing dismissed the allegations, saying its personnel were aiming to block an "illegal transportation" of supplies. "No direct measures" were taken against the Filipino soldiers, foreign ministry spokesman Lin Jian told reporters in Beijing.
"Law enforcement measures taken by the China Coast Guard at the site were professional and restrained," he added.
In an earlier statement, the Chinese coast guard said the Philippines was "entirely responsible" for the incident, as troops “ignored China’s repeated solemn warnings... and dangerously approached a Chinese vessel in normal navigation in an unprofessional manner, resulting in a collision”.
China has routinely attempted to block re-supply missions to the shoal. Filipino officials say the Chinese employ "dangerous manoeuvres" such as shadowing, blocking, firing water cannons and shining lasers to temporarily blind Filipino crews.
Monday's confrontation took part in an area at the heart of the sea encounters: the Filipino outpost in Second Thomas Shoal, where the country grounded a decrepit navy ship to enforce its claim.
A handful of soldiers are stationed there and require regular rations.
Analysts say choking the flow of supplies to the outpost, which could lead to its collapse into the sea, would allow Beijing to take full control of the area.
Observers fear any escalation in the South China Sea could spark a conflict between China and the US as it is treaty-bound to come to the Philippines' defence, should it come under attack.
Philippine President Ferdinand Marcos warned security forum in Singapore last month that if a Filipino died as a result of China’s wilful actions, Manila would consider it as close to “an act of war” and would respond accordingly.
But Gen Brawner said the Philippines military did not want to spark a war.
"Our objective is that while we want to bring supplies to our troops following international law, our objective is to prevent war," he said.