North Korea appears to have restarted its Yongbyon nuclear reactor, the UN atomic agency has said in a report.

Plutonium, which is used for nuclear weapons, is believed to be produced at the reactor's complex.

The International Atomic Energy Agency (IAEA) was expelled by Pyongyang in 2009 but relies on satellite imagery to carry out assessments.

The watchdog said the reactor has been discharging cooling water since July, suggesting it is operational.