North Korea may have reactivated a plant for reprocessing plutonium for use in nuclear weapons, the UN atomic watchdog said Monday, citing satellite imagery and echoing recent comments from a US think-tank.

"The indications that we have obtained... (are of) activities related to the five-megawatt reactor, expansion of enrichment facilities and activities related to (plutonium) reprocessing," International Atomic Energy Agency head Yukiya Amano said.