In what appears to be a clear message of its military might, China has staged the first test flight of its new stealth jet.

The J-20 is thought to be years from entering active use in the superpower's airforce but its test run seemed impeccably timed, with U.S. defence chief Robert Gates in Beijing on the second day of an official visit.

The fighter jet's successful test follows reports that China is planning to launch its first aircraft carrier and has tested a ballistic missile capable of sinking U.S. vessels in the Pacific.

The J-20 flew for about 15 minutes over an airfield in the southwestern city of Chengdu on Monday, the same site where the aircraft carried out high-speed runway taxi tests last week.

The prototype jet was shown in flight, with civilians and air force personnel watching on, in pictures on several unofficial Chinese military websites, after local media outlets had claimed a successful test flight had taken place.

While the Chinese government is renowned for its stringent approach to state secrets, photos and reports of the J-20's test have remained online.

According to international agencies, the scheduling of the test flight to coincide with Mr Gates' visit to China, coupled with the seemingly relaxed approach to reports about the flight, indicate Beijing's willingness to be more open about its military intentions.

Nonetheless, reports of the stealth's successful test will do little to quell anxieties about the speed of China's military progress.

The U.S. F-22 Raptor is currently the only operational stealth fighter in the world, while Russia's Sukhoi T-50 jet is expected to enter active service in the next four years.

But pictures of China's J-20, which looks larger than the F-22 or T-50, will be of concern to the Taiwanese government, whose antiquated aircraft and radar systems would provide little resistance to radar-evading Chinese jets.

The U.S. has claimed China would not be capable of developing a stealth jet for years and production of the F-22 was recently capped.

But the J-20's successful test, coupled with reports of the development of an aircraft carrier and missile system, confirms China's growing military might.