North Korea has announced it will restart the facilities at its main Yongbyon nuclear complex, including a reactor mothballed in 2007.
In a statement, it has been announced that the move would bolster North Korea’s nuclear forces “in quality and quantity”.
The move is the latest in a series of measures by Pyongyang in the wake of its third nuclear test in February 12.
North Korea has been angered by the resultant UN sanctions and joint US-South Korea annual military drills.
In recent weeks North Korea has issued a series of threats against both South Korean and US targets, to which the US has responded with high-profile movements of advanced aircraft and warships around the Korean peninsula.
The reactor at Yongbyon – which was the source for plutonium for North Korea’s nuclear weapons programme – was closed in July 2007 as part of a disarmament-for-aid deal.
The cooling tower at the facility was later destroyed, but then the disarmament deal stalled.
Part of the reason the agreement fell apart was because the US and North Korea’s other negotiating partners did not believe Pyongyang was fully disclosing all of its nuclear facilities.
The statement, carried by KCNA news agency, was attributed to a spokesman for the General Department of Atomic Energy.
The General Department of Atomic Energy had decided “to adjust and alter the uses of the existing nuclear facilities” including “readjusting and restarting all the nuclear facilities in Nyongbyon [Yongbyon]”.
The work would be put into practice without delay, the statement said.