Photographs showing Kim Jong-un proudly watching as a North Korean missile was launched from an underwater submarine were manipulated by state propagandists, experts claimed on Tuesday.

German aerospace experts said photos of the launch were "strongly modified", including reflections of the missile exhaust flame in the water which did not line up with the missile itself.

German experts suspect this photo of Kim Jong-un has been altered. Credit:KCNA

"Considering the track record of North Korean deceptions, it seems sensible to assume that any North Korean SLBM [submarine-launched ballistic missile] capability is still a very long time in the future, if it will ever surface," Markus Schiller and Robert Schmucker, of Schmucker Technologie, told Reuters.