Philippines warns China as joint war games with US start

11,600 US, Philippine and Australian troops will take part. Photo / AP

More than 11,000 soldiers from the Philippines, United States and Australia will take part in joint drills in the South China Sea, as the Philippines' military chief called China's building work on disputed reefs "worrisome" and a source of friction with its neighbours.

The reclamation "will cause tensions among claimant countries not only because it could deter freedom of navigation but also because of its possible military purposes," General Gregorio Pio Catapang said.

China must "stop the reclamation activities and be mindful of its responsibilities as a claimant state and an important member of the international community."

The comments come as 11,600 Filipino, US and Australian soldiers - twice as many as last year - are set to join the war games off Palawan province near contested South China Sea islands.

Disputes over the sea, of which China claims about four-fifths under a so-called nine-dash line drawn on a 1940s map, have escalated as China expands the reach of its military to back its territorial interests.

The military drills, which run until April 30, seek to "improve our interoperability and enhance our national defence capability", Foreign Affairs Undersecretary Evan Garcia told reporters after the opening of the annual Balikatan war games.

"Our armed forces needs to improve its own capacity in order to better serve and protect our country."

Catapang said the drills are not directed against China. He said a US plan to deploy advanced air force and naval equipment in the Philippines was in the works.

"We will offer them facilities that we can jointly use because of the situation now obtaining in the West Philippine Sea," Catapang said, referring to the South China Sea.

China has often stated its right to carry out construction work in the South China Sea, with recent satellite photos showing Chinese dredgers at work at Mischief Reef in the Spratly Islands, a feature also claimed by Vietnam, the Philippines and Taiwan.

Catapang also accused China of tolerating harmful fishing practices by its fishermen in Scarborough Shoal.