The US has warned China that there will be consequences for its growing militarisation in the South China Sea, the media reported.

This was following reports of missiles being deployed to three of the country's outposts in the disputed region, CNN reported.

"We're well aware of China's militarisation of the South China Sea. There will be near-term and long-term consequences," White House Press Secretary Sarah Sanders said on Thursday.

The US intelligence assessed that there is a high probability the Chinese military had deployed anti-ship and anti-aircraft missiles during the military drills on the contested sea.

The South China Sea is one of the most contested regions in the world, with overlapping territorial claims by China, the Philippines and Vietnam, among several others.