North Korea has successfully miniaturised nuclear warheads which can be mounted on ballistic missiles, according to the repressive regime's leader, Kim Jong-Un.
State media reports suggest Mr Kim has called for his military to be on standby to mount pre-emptive attacks against South Korea and the US - and be prepared to use nuclear weapons.
The inflammatory remarks came after new sanctions were imposed on North Korea by the United Nations.
Those new economic restrictions were in response to the country's fourth nuclear test in January, when officials claimed they had set off a miniaturised hydrogen bomb, and the launch of a long-range rocket last month.
This is the first time Mr Kim has directly mentioned the previously reported claims of miniaturised nuclear warheads, which have been questioned by some security experts.
After inspecting the progress of nuclear workers, the Supreme Leader said he was "greatly pleased" with their achievements, which could be regarded as a "true nuclear deterrent".
Meanwhile, a UN panel has said it has "serious questions about the efficacy of the current UN sanctions regime" against North Korea - with experts warning that the country has been "effective in evading sanctions".
Their report said this was because some UN Security Council member states had a "lack of political will" to implement them effectively - or regarded their enforcement as a "low priority".