UN atom chief has great concern over North Korea

Revelations about North Korea's expanded nuclear programme are of "great concern", UN atomic watchdog chief Yukiya Amano said on Thursday.

North Korea boasted about its nuclear advances earlier this week saying it was operating a uranium enrichment plant with thousands of centrifuges, which could offer the reclusive state a second pathway to make a nuclear bomb.

"It was with great concern that I learned of recent reports about the new uranium enrichment facility, as well as the construction of a light water reactor, in (North Korea)," Amano told the International Atomic Energy Agency's governing board.