The standoff over Sandy Cay, which lies close to military outposts built by both Beijing and Manila, was the latest between the two nations.

Both countries have planted flags on a collection of sand bars, extending the clash over the area between Beijing and Manila, a U.S. ally

China has asserted sovereignty over an uninhabited reef in the South China Sea by planting a flag, according to state media, setting the stage for an escalation of tensions with the Philippines over the disputed area.