Philippine President Rodrigo Duterte has ordered troops to live on up to 10 unoccupied islands and reefs in the South China Sea in a dramatic reversal of policy on the flashpoint waters.

Only six months after declaring his "separation" with the United States and "realignment" with China, Mr Duterte said the Philippines needs to assert its jurisdiction over areas it claims, a move likely to provoke rival claimants, including China.

"It looks like everybody else is making a grab for the islands there, so we better live on those that are vacant," the President told reporters during a visit to a military camp on the western island of Palawan.

"I have ordered the armed forces to occupy all… at least, let us get what is ours now and make a strong point there that it is ours."