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.

The Philippine Coast Guard condemned "dangerous" manoeuvres by a Chinese Navy helicopter Tuesday as it flew within three metres (10 feet) of a surveillance flight carrying a group of journalists over the contested Scarborough Shoal.