A video released by the Philippine military appears to show Chinese and Filipino boats clashing in the contested waters of the South China Sea.
The Philippines has accused Chinese vessels of ramming Philippine boats, then boarding them and seizing weapons.
The country's top military commander General Romeo Brawner said Chinese coast guard personnel were armed with swords, spears and knives.
This appears to be an escalation, after a series of dangerous encounters, as the two sides seek to enforce their claims on disputed reefs and outcrops.
The confrontation took place as the Philippine navy and coast guard were delivering supplies to Filipino troops stationed in the Second Thomas Shoal, a decrepit navy ship used as a Filipino outpost.
Beijing said its personnel were professional and restrained, adding that they were aiming to block an "illegal transportation" of supplies.