The Philippine coast guard (PCG) said its vessel was assisting a navy mission to deliver food and supplies to troops on an atoll in the disputed waterway on February 6 when a Chinese coast guard ship directed a "military-grade laser" at the ship, temporarily blinding its crew on the bridge.
"I think it's time for the Chinese government to restrain its forces so that it does not commit any provocative act that will endanger the lives of people," military spokesman Medel Aguilar told reporters.
Aguilar quoted the Philippine defence chief as saying the Chinese action was "offensive" and unsafe.
The incident took place at the Second Thomas Shoal, 105 nautical miles (195km) off the Philippine province of Palawan.Â
The shoal is home to a small Philippine military contingent on board a rusty ship.
The 100-metre-long World War II ship was intentionally grounded on the shoal, known in the Philippines as Ayungin, in 1999 to reinforce Manila's sovereignty claims in the Spratly archipelago.
"The deliberate blocking of the Philippine government ships to deliver food and supplies to our military personnel ... is a blatant disregard for, and a clear violation of, Philippine sovereign rights," the PCG said in a statement.
China's foreign ministry said in response that its coast guard conducted actions according to the law.
"We urge the Philippines to avoid such actions, and the actions of China's staff are professional and restrained," China's foreign ministry spokesman, Wang Wenbin, told a regular briefing.
The PCG did not elaborate on what a "military grade laser" was but images it supplied showed green light emanating from a Chinese vessel with bow number 5205.
The office of Philippine President Ferdinand Marcos declined to comment, referring reporters to the PCG statement.
Marcos visited Beijing last month when China said it was ready to manage maritime issues "cordially".
It is not the first time China has been accused of using lasers in the region.
In February last year, Australia accused China of an "act of intimidation" after a Chinese navy vessel directed a laser at an Australian military surveillance aircraft.
The reported bid to block the Philippine resupply mission comes as Marcos has expressed openness to forging a visiting forces agreement (VFA) with Japan to boost maritime security.
Marcos visited Japan last week to strengthen security ties.
Close United States ally Japan in December announced its biggest military-build up since World War II, fuelled by concern about aggressive Chinese action in the region.
The Philippine president also recently granted former colonial power the US access to more military bases under a VFA, which China said undermined regional stability and raised tensions.
The agreement with the US provides rules for the rotation of thousands of US troops in and out of the Philippines for exercises.
