The Philippines said the China Coast Guard fired water cannon and "sideswiped" a government vessel Wednesday during a maritime patrol near the disputed Scarborough Shoal, after Beijing said it had "exercised control" over the ship.
China claims almost the entire South China Sea, brushing off rival claims from other countries -- including the Philippines -- and an international ruling that its assertion has no legal basis.
Vessels from the two sides have clashed frequently in the past year, resulting in injuries and damages.
Tensions flared again on Wednesday, with Manila releasing a video appearing to show a Chinese coast guard hitting the right side of fisheries department vessel BRP Datu Pagbuaya, with the crew shouting, "Collision! Collision!".
The Chinese ship "fired a water cannon... aiming directly at the vessel's navigational antennas", the Philippine coast guard and fisheries ministry said in a joint statement.
The Chinese vessel then "intentionally sideswiped" the ship before launching a second water cannon attack, the statement said.
China's coast guard said in a statement that Philippine ships "came dangerously close" and that its actions had been "in accordance with the law", but gave no further details about the manoeuvres it used during the incident.
"On December 4, Philippine Coast Guard ships... attempted to intrude into China's territorial waters around Huangyan Island," coast guard spokesperson Liu Dejun said, using the Chinese name for Scarborough Shoal.
The shoal -- a triangular chain of reefs and rocks -- has been a flashpoint between the countries since China seized it from the Philippines in 2012.
Since then, Beijing has deployed patrol boats that Manila says harass Philippine vessels and prevent Filipino fishermen from accessing a fish-rich lagoon there.
The shoal lies 240 kilometres (150 miles) west of the Philippines' main island of Luzon and nearly 900 kilometres from the nearest major Chinese land mass of Hainan.
- Growing tensions -
Tensions between Manila and Beijing in the South China Sea escalated last month when Philippine President Ferdinand Marcos signed two laws defining the country's sea waters and imposing fixed lanes for foreign ships, prompting China to summon the Philippine ambassador.
And ties frayed further when the Philippines and the United States signed a security deal allowing both sides to share classified information.
In a separate incident, Beijing said Monday it had taken "control measures" against Philippine ships it accused of "illegally gathering" near Iroquois Reef in the disputed Spratly Islands.
On that occasion, Beijing warned Manila to "immediately stop its infringements and provocations".
Manila said a Chinese navy helicopter had "harassed" Philippine fishing vessels in the area, and shared video footage that purported to show the aircraft hovering low over a Philippine boat.
The Philippine coast guard said it had deployed two vessels in the area "to ensure the safety and security of Filipino fishermen exercising their right to fish freely" there.