A satellite image has also shown 'suspicious activity' at a nuclear enrichment site in the DPRK. The monitor group says plumes of exhaust steam, a byproduct of heating the main plant at the Yongbyon Radiochemical Laboratory complex, have been seen in commercial satellite images taken March 12 and over the preceding five weeks.

The report by the Washington, D.C.-based project says the activity is unusual.It says the plumes of steam do not necessarily indicate that the process for refining plutonium for nuclear weapons is underway or will be soon.

However, U.S. Director of National Intelligence James Clapper recently testified that Pyongyang had “announced its intention to ‘refurbish and restart’ its nuclear facilities,” including the uranium enrichment facility at Yongbyon.