North Korea could soon be resuming production of its nuclear weapons.
In its annual report dated Friday, the International Atomic Energy Agency said Pyongyang appeared to have restarted a nuclear reactor believed to have once produced plutonium for the country's nuclear arsenal.
It said in its report that, for two and a half years, there had been no indications of that reactor's operation at Yongbyon, a complex at the heart of Pyongyang's nuclear program until July.
It added that the apparent restart of the reactor coincides with indications of activity at a nearby uranium mine and plant.
That comes after the IAEA said there had been signs at Yongbyon of possible reprocessing work to separate plutonium from spent reactor fuel earlier this year.
The IAEA - which is the UN's atomic watchdog - called the new indications 'deeply troubling'.
It monitors North Korea from afar, largely through satellite imagery, after its inspectors were expelled by Pyongyang in 2009.