MOSCOW (AFP) - Russia said on Thursday that North Korea was apparently conducting work on a nuclear reactor, saying the aged facility was in such a "nightmarish state" it could cause a disaster.

"It is obvious that some works are being conducted, and for a long time at that. According to some signs, steps were indeed being taken to relaunch it," the Interfax news agency quoted a diplomatic source as saying.

"But we do not have any information that the reactor has been relaunched... The reactor is in a nightmarish state, it is a design dating back to the 1950s... For the Korean peninsula this could entail terrible consequences, if not a man-made catastrophe."