A Chinese navy helicopter has flown within 10 feet of a Philippine patrol plane in a disputed area of the the South China Sea, highlighting Beijing's use of force in asserting its claims to the strategic waterway.

A Philippine plane warned a Chinese military helicopter over the South China Sea that it was "flying too close," as tension between the U.S. ally and Beijing soars.

Manila says it will lodge a diplomatic protest after a Chinese helicopter came within 3 metres of a Philippine plane.