Image copyright Reuters Image caption Chinese media said the US vessel "posed a threat to China's military security"

China says one of its warships "encountered" a US vessel, confirming US reports of a near-collision in the South China Sea earlier this month.

The US said its guided missile cruiser USS Cowpens was forced to take evasive action as the two ships neared each other on 5 December.

It has been described as the most serious Sino-US confrontation in the South China Sea since 2009.

However, China said the incident was handled with "strict protocol".

The US has said its ship was operating in international waters.

But China claims parts of the South China Sea, and a state-run newspaper quoted an expert as saying that the US boat had been "harassing" China's aircraft carrier, the Liaoning, as it carried out drills.

'Strict protocol'

The incident came to light last week after US officials spoke about it.

"While lawfully operating in international waters in the South China Sea, USS Cowpens and a PLA [People's Liberation Army] Navy vessel had an encounter that required manoeuvring to avoid a collision," a US Pacific fleet statement said.

Analysis What happened in the South China Sea on 5 December? The US has one story and China has another. Were the Americans "harassing" a cluster of Chinese naval ships, as Chinese media reports have suggested? Or was China out of line by attempting to cordon off a disputed section of the South China Sea for an entire month while it took its new aircraft carrier, the Liaoning, out for a spin? After confirming a near-miss took place, both countries appear to be downplaying the incident, emphasising the strong military ties between Beijing and Washington. Indeed, China's navy is still set to participate in the international Rim of the Pacific war games near Hawaii next year. But tensions are still bubbling. China will continue to assert its claims to large swathes of the South and East China Seas - areas that other regional neighbours claim as their own. The US says it is trying to stay away from such disagreements, but it asserts its right to travel through what it considers to be international waters. Until these territorial spats are settled, or a status quo is accepted, smooth sailing in the waters near China might be difficult indeed.

Eventually, the two crews were able to communicate and "both vessels manoeuvred to ensure safe passage", an unnamed defence official was quoted by Reuters as saying.

The US had raised the incident at a "high level" with China, an unnamed State Department official quoted by US military newspaper Stars and Stripes said.

In a statement on Wednesday, China's defence ministry said the two ships met during a "routine patrol" by one of China's naval vessels.

"The Chinese naval vessel strictly followed protocol and handled the incident," it said.

"The two defence departments used normal working channels to stay informed about the situation and communicated effectively."

The statement added, without elaborating, that some media reports about the event were untrue.

On Monday, China's state-run newspaper Global Times said the US vessel had "posed a threat to China's military security", and quoted an unnamed source as saying that USS Cowpens had been "tailing after and harassing" the Liaoning.

The Liaoning - which is China's first aircraft carrier - was making its first voyage into the South China Sea, an area in which Beijing has multiple overlapping territorial claims with South East Asian nations.

The incident came amid tensions after China established an air defence identification zone (ADIZ) over a swathe of the East China Sea, including disputed islands controlled by Japan.

Japan, the US and South Korea - which claims a rock that lies within China's declared zone - have strongly criticised the move, with the US calling it "an attempt to unilaterally change the status quo" in the region.

On Tuesday, US Secretary of State John Kerry said the East China Sea air zone should not be implemented and "China should refrain from taking similar, unilateral actions elsewhere in the region and in particular, over the South China Sea."

In 2009, the US government said five Chinese ships "aggressively manoeuvred" close to an unarmed US navy surveillance vessel in international waters in the South China Sea.

However, China described the US reports as "totally inaccurate" and said the ship was conducting activities within China's exclusive economic zone.