The Philippines called on Beijing on Saturday to "immediately cease all provocative and dangerous actions" after accusing it of "unjustifiably" deploying flares from China-occupied Subi Reef on August 22 while a Manila aircraft was conducting patrols.
The same aircraft also "faced harassment" from a Chinese jet fighter while it was conducting a surveillance flight near Scarborough Shoal on August 19, the Philippines' South China Sea Task Force said in a statement.
"Such actions undermine regional peace and security, and further erode the image of the PRC (People's Republic of China) with the international community," the task force said.
There was no immediate comment from the Chinese Embassy in Manila about the incidents, which happened the same week Manila and Beijing accused each of ramming vessels and performing dangerous maneuvers in the South China Sea.
They also came less than two weeks after an air incident between the Chinese and Philippines militaries in Scarborough Shoal, even as the two nations have agreed to "restore trust" and "rebuild confidence" to better manage maritime disputes.
Manila's aircraft, which belonged to the Bureau of Fisheries and Aquatic Resources (BFAR), in coordination with the coast guard, was tasked to monitor and intercept poachers encroaching on the Philippines' exclusive economic zone.
The task force said the Chinese jet fighter, which was not provoked, deployed flares multiple times "at a dangerously close distance" from the BFAR aircraft.
"Its actions demonstrated hazardous intent that jeopardized the safety of the personnel onboard the BFAR aircraft," the task force said.
China claims sovereignty over nearly the whole South China Sea and has deployed an armada of coast guard vessels to protect what it considers its territory. The Philippines, Taiwan, Malaysia, Indonesia, Vietnam and Brunei contest the claims.
An international arbitral tribunal in 2016 said Beijing's claim has no basis under international law, awarding a landmark victory to the Philippines which filed the case.
China has built seven artificial islands in the South China Sea, and equipped some with radar, runways and surface-to-air missiles. Those include Subi Reef just 24 kilometers away and visible from Thitu, the most strategically important of nine features the Philippines occupies in the Spratlys.
"We firmly reiterate our call on the government of the People's Republic of China to immediately cease all provocative and dangerous actions that threaten the safety of Philippine vessels and aircraft engaged in legitimate and regular activities" within the country's EEZ, the task force said.
