PYONGYANG (THE KOREA HERALD/ASIA NEWS NETWORK) - North Korea could have manipulated images of its latest rocket launches, a German rocket expert recently said on a US radio show.

Dr Markus Schiller, who specialises in mechanical and aerospace engineering, raised the suspicions on Voice of America on Monday (March 30).

"If you measure the dimensions of the missile which just seems to have left the launch tube, the missile is too large, diameter is too big and the length is too long to fit into that launch tube," he said.

North Korea test-fired what it claimed to be two super-large rockets on Sunday, and the next day released a set of photographs as proof of a "successful" test.

Dr Schiller, however, said the flame and lighting surrounding one of the rockets captured in the photograph look unnatural.

"Some smoke in the background, but it is only in the background. The launcher is not enveloped in smoke and you can clearly see the very bright burning back of the missile, but it doesn't affect the rest of the photos. It just doesn't look natural," the expert said.

Another North Korean expert said it was too early to rule that the photo had been doctored, but it raised suspicions because Pyongyang was y unwilling to release many launch pictures.

"They're being really weird about this. They're not showing us nearly as many pictures of this system as they are showing us of the wheeled one and I don't know why that is," said Dr Jeffrey Lewis of the Middlebury Institute of International Studies in the US, referring to Pyongyang's earlier launches.

Meanwhile, other missile experts said it was more suspicious that North Korea underwent a series of weapons tests involving super-large rockets, Washington-style ballistic missile ATACMS and Moscow's ballistic missile Iskander.

"North Korea doesn't have a lot of industry… it makes no sense for them to be producing three different kinds of missiles that all do basically the same thing. Huge inefficiency," said Mr Ian Williams, deputy director of the Missile Defence Project at CSIS.

Dr Bruce Bennett, a senior defence researcher at the Rand Corp, said the unprecedented flurry of launches was aimed to capture publicity amid denuclearisation negotiations being deadlocked since bilateral talks between the US and North Korea broke down in October last year.