The Philippines accused China's coast guard of firing water cannon and using a "dangerous maneuver" on Thursday to block vessels bringing aid to Filipino fishermen near a disputed South China Sea reef.
The incident took place near Scarborough Shoal, hours before Manila hosted a regional security forum attended by the top diplomats of both China and the United States, AFP reported.
It was the second incident involving the two Asian neighbors in four days, after a relatively peaceful few months.
Beijing claims most of the South China Sea, including the flashpoint shoal, despite an international ruling that its assertion lacks any legal basis.
On Thursday, the Philippine Coast Guard said a China Coast Guard ship closed to within 50 meters (164 feet) of the BRP Datu Dumangsil and fired water cannon at it for two minutes.
Half an hour later, a second Chinese coast guard vessel crossed 500 meters across the bow of Dumangsil's sister vessel Datu Paiburong in what the Philippine statement called a "dangerous maneuver".
China Coast Guard spokesman Jiang Lue said the Filipino vessels "intruded into the jurisdictional waters of China's Huangyan Island despite... repeated dissuasions and warnings".
"The China Coast Guard took necessary measures, including tracking, monitoring, blocking, and controlling the Philippine vessels in accordance with the law, and expelled them," he said.
Neither Filipino vessel was hit, and they continued their mission to supply fuel to Filipino fishermen in the area, a Philippine coast guard official told AFP.
Scarborough Shoal is a fish-rich reef formation 240 kilometers (124 miles) from the main Philippine island of Luzon and hundreds of kilometers away from mainland China.
In a Monday clash, the Philippine military accused China Coast Guard personnel of clubbing a Filipino sailor with a baton near the disputed Second Thomas Shoal.
China said the Philippines had instigated the incident near a grounded vessel that has long served as a Philippine garrison.
Both countries summoned each other's ambassadors on Tuesday following the clash, which sparked condemnation of Beijing by Manila's allies.
Maritime security issues are high on the agenda of the ongoing meetings of the Association of Southeast Asian Nations (ASEAN) and other countries.
ASEAN members have long sought to reach a code of conduct with China for the waterway.
