Chinese military observers have dismissed recent speculation over the development of China's second stealth fighter J-21, after military fans posted pictures of a mysterious airframe covered by camouflage online.

Videos and photos posted on the forum defensecn.com in late June showed a truck carrying the airframe traveling from Shenyang, Northeast China's Liaoning Province, where the AVIC Shenyang Aircraft Corporation is located, to Yanliang, Northwest China's Shaanxi Province, home to the Chinese Flight Test Establishment.

Military fans believed it was a fifth-generation fighter J-21, which is nicknamed "Snowy Owl," and speculated that it would take test flights or wind tunnel tests in September.

Japan's The Diplomat magazine earlier this month commented that it is not impossible for China to develop another stealth aircraft while struggling with the J-20 developed by the Chengdu Aircraft Industry Corporation, especially if the aircraft are to play different roles.

It quoted Roger Cliff, who co-authored the RAND monograph, as saying that the J-20 would perform the role of a penetrating strike aircraft and the J-21 that of an air superiority fighter.

The magazine also said some experts believe the rumored J-21 could be a carrier-based stealth aircraft, while others point to its role as an export item to compete with the US light fighter F-35.

Meanwhile, Chinese military experts are still being cautious about the camouflaged airframe.

"The rumors on the Internet are not trustworthy," Li Daguang, a military expert at the PLA National Defense University, told the Global Times, adding that as far as he knows, there is no such new model.

Song Xiaojun, a military expert, told the Global Times that he also noticed the photos of the rumored plane, but added it was hard to say what it is.

"It might just be a model made of iron or wood. All the speculation is based on hearsay," Song said.

China's first stealth fighter, the J-20, has two prototypes. The new prototype 2002 has been conducting rounds of test flights in Chengdu, Sichuan Province since May.