MANILA -- An official said the Philippines has filed a low-key diplomatic protest with China after a US think tank reported that Beijing appears to have installed anti-aircraft and anti-missile weapons on its man-made islands in the strategically vital South China Sea.

Foreign Secretary Perfecto Yasay said Monday that a note verbale was issued after the report came out last month.

The Center for Strategic and International Studies report said that anti-aircraft guns and close-in weapons systems designed to guard against missile attack have been placed on all seven of China's newly created islands.

Yasay said in an interview with CNN Philippines that Manila had responded, but did so quietly as taking more aggressive moves would not help resolve the problem. (AP)