China has carried out its first flight test of a fifth-generation J-20 stealth fighter jet, Chinese President Hu Jintao has confirmed to US Defense Secretary Robert Gates.

The confirmation comes after several leaked images of the aircraft appeared on multiple unofficial Chinese websites with the Pentagon playing down concerns over the fighter.

The J-20 is a single-seat, twin-engine aircraft, which appears to be larger and heavier than the Sukhoi T-50 and Lockheed Martin F-22 Raptor.

Russia and China have reportedly been working on prototypes of stealth fighters, which are invisible to radar.

China expects the stealth aircraft to be operational with the Chinese Air Force between 2017 and 2019, reports BBC News.