The Philippines is demanding an explanation from Beijing, after the Chinese coast guard allegedly fired a water cannon at Filipinos fishing in a disputed area of the South China Sea.
Manila on Tuesday summoned China's top envoy in the Philippines' capital to protest the incident, which happened last month near the uninhabited Scarborough Shoal. The rocky outcrop has become a flashpoint in military tensions between both countries.
Foreign ministry spokesman Raul Hernandez said Manila "strongly protests the acts of harassment" in the January 27 incident and called on China to respect the rights of Philippine fishermen in the area.
"These actions, these incidents, surely escalates the tension in the area and this further threatens the peace and security and stability in the region."
Philippine President Benigno Aquino said he does not want to overreact to what may be a "one-off incident," but would like to know whether the case reflects a new Chinese policy.
In response, Chinese foreign ministry spokeswoman Hua Chunying said Beijing "does not accept protestations from the Philippine side." She insisted the purpose of the sea patrols are to "uphold China's sovereignty."
In recent years, many of China's neighbors have complained of what they say is its aggressiveness in defending claims to disputed maritime areas.
Earlier this year, China rattled the region by demanding all foreign fishing vessels ask permission to enter more than half of the 3.5-million-square-kilometer South China Sea.
Parts of the resource-rich, strategic waterway are also claimed by Vietnam, Malaysia, and Brunei.
In 2012, China and the Philippines were engaged in a tense standoff over the Scarborough Shoal. Manila eventually withdrew its ships, but took the dispute to the United Nations International Tribunal on the Law of the Sea.
This angered Beijing, which prefers to solve the maritime disputes with one-on-one discussions and not international arbitration or multilateral forums.