BEIJING (REUTERS) - China's first and only aircraft carrier has successfully carried out a series of tests during a training mission in the disputed South China Sea, state media reported on Monday.

This month's drills off the coast of Hainan Island mark not only the first time China has sent a carrier into the South China Sea but the first time it has manoeuvred with the kind of strike group of escort ships US carriers deploy, according to regional military officers and analysts.

The Liaoning has carried out more than 100 tests, including of its combat systems, and training tasks since early December, the official English-language China Daily said.

"The Liaoning successfully performed several tests of the combat system today and organised for the first time comprehensive combat training," the newspaper cited the navy saying in a statement.

"Through this operation, we tested the carrier's combat capability and tried the performance of its propulsion and seaworthiness."

The mission has been characterised by "a large number of tests, rigorous standards, complicated circumstances as well as collaboration with multiple military units", it added.

The carrier is being escorted by two destroyers and two frigates.

"The South China Sea has deep waters, strong wind and big waves, making it a suitable place for the aircraft carrier to conduct tests and training," the China Daily quoted the Liaoning's captain, Zhang Zheng, as saying.

Zhang said drills included practicing defending against hostile aircraft, ships and submarines in simulations.

The Liaoning - a Soviet-era ship bought from Ukraine in 1998 and re-fitted in a Chinese shipyard - has long been a symbol of China's naval build-up.

After two decades of double-digit increases in the military budget, China's admirals plan to develop a full blue-water navy capable of defending growing economic interests as well as disputed territory in the South and East China Seas.

Carrier strike groups sit at the core of those ambitions - and successfully operating the 60,000-tonne Liaoning is the first step in what state media and some military experts believe will be China's deployment of several locally built carriers by 2020.

The USS Cowpens narrowly avoided colliding with a Chinese warship escorting the Liaoning while operating in international waters on Dec. 5, the US Navy has said.

US Defence Secretary Chuck Hagel on Thursday called the Chinese ship's actions "irresponsible".

China's official Xinhua news agency said the Cowpens was "warned" by the carrier task force, adding the US vessel was "intentionally" putting the Liaoning under surveillance.