A Chinese Navy ship was spotted shadowing Philippine and United States vessels conducting joint patrols in the West Philippine Sea, Armed Forces of the

Philippines Chief General Romeo Brawner Jr. revealed on Thursday.

Brawner said the People's Liberation Army Navy ship was monitored within 30 nautical miles of the Malampaya gas field in northern Palawan past 10 a.m. on Thursday.

"There was shadowing. We monitored a Chinese vessel shadowing the joint maritime patrol but there were no aggressive actions by China," he said in a chance interview with reporters. 

The PLA vessel was tailing the Philippine and US ships "from approximately 6.5 nautical miles away," he said, adding that the Chinese ship did not issue a radio challenge or engage in "dangerous maneuvers."

China Coast Guard and Chinese militia vessels have been harassing Philippine Coast Guard and Philippine Navy ships, as well as Filipino fishermen, in the West Philippine Sea, which Beijing claims as part of its territory.

A 2016 arbitral ruling affirmed the Philippines' entitlement in the WPS while it shot down China's claim to nearly the entire South China Sea.

"They were just shadowing us," Brawner said. "The joint maritime and air patrols between the Philippines and the US have been very successful in the sense that there were no untoward incidents during the activity."

Interoperability test

"We were able to achieve the objectives that we had set forth for this joint maritime and air patrol. So, we have seen how we can operate closely with our allies, (like) the United States," the AFP chief said.

The joint patrols are being conducted to test the interoperability of US and Philippine forces.

Brawner said they have yet to discuss the possibility of allowing the US to join the AFP's maritime missions to the country's occupied features in the WPS.

"Well, we have not talked about that yet, we just discussed this particular joint maritime and air patrol," he said.