The Philippines has filed a diplomatic protest with China, its foreign minister said on Monday, over Beijing's installation last year of anti-aircraft and anti-missile systems on its man-made islets in the disputed South China Sea.

The protest note was sent to the Chinese Embassy in December, after confirmation of a report from the U.S.-based Center for Strategic and International Studies about a weapons buildup on seven artificial islands in the Spratlys.

One of those islands is located within the Philippines' 200-nautical-mile exclusive economic zone.