First flown in 2011, the J-20 is China's answer to fifth-generation jets such as the U.S. F-22 and F-35

BEIJING: China's home built J-20 stealth fighter has conducted sea training for the first time, the air force said Wednesday.

The recent mission took the plane or planes out to sea for drills under ``actual war conditions,'' air force spokesman Senior Col. Shen Jinke posted to the service's micro-blog. He called that a ``further upgrade of the air force's combat capabilities.''

China said in February that the plane had obtained initial operational capability and was being introduced into combat units.

First flown in 2011, the J-20 is China's answer to fifth-generation jets such as the U.S. F-22 and F-35.

With its stealthy capabilities, speed and manoeuvrability, it potentially represents a major upgrade to Chinese air power, although questions have been raised about some of its technologies, especially its engines.

Though developed domestically, the J-20 is believed to rely on Russian engines for propulsion.

China increased its defence budget by 8.1 percent this year to 1.1 trillion yuan ($173 billion), as it prepares to launch its second aircraft carrier and field an array of advanced warplanes and missiles able to attack air and sea targets at vast distances.