North Korea expands nuclear weapons programme
North Korea's parliament has endorsed plans to give nuclear weapons greater prominence in the country's defences.
The move came a day after the ruling Workers' Party called for nuclear forces to be "expanded and beefed up qualitatively and quantitatively".
North Korea has said it is entering a "state of war" with the South - prompting Seoul to promise a "strong response" to aggression by the North.
The North is angry at UN sanctions following its nuclear test in February.
It is also unhappy with joint US-South Korea annual military drills. But the US says there is no sign of North Korean "actions to back up the rhetoric".
Meanwhile, North Korea has announced it has appointed a new premier, Pak Pong-ju. He was sacked from the same post in 2007.
'The nation's life'
North Korea's Supreme People's Assembly convened on Monday for a day-long annual session. It normally focuses on making economic decisions.
But state news agency KCNA said the body had "unanimously adopted an ordinance that provides for giving nuclear weapons greater prominence in the defence of the country".
The law reads that the country's nuclear weapons are a "means of defence" and serve the purpose of "dealing deadly retaliatory blows at the strongholds of aggression until the world is denuclearised".
On Sunday the Workers' Party Central Committee held a rare high-level meeting in which it described nuclear weapons as "the nation's life".
"The DPRK [North Korea]'s possession of nuclear weapons should be fixed by law and the nuclear armed forces should be expanded and beefed up qualitatively and quantitatively," a KCNA report on the meeting said.
"The People's Army should perfect the war method and operation in the direction of raising the pivotal role of the nuclear armed forces in all aspects concerning war deterrence and war strategy."
In the last few days North Korea has issued multiple warnings of attacks on US and South Korean targets - to which the US has responded with an apparent show of military hardware. The US flew F-22 planes from Japan to South Korea's Osan Air base on Sunday, as part of ongoing joint military exercises with Seoul, officials said.
Speaking to defence officials on Monday, South Korean President Park Geun-hye said that she took the series of threats from Pyongyang "very seriously".
But despite its rhetoric few think the North - which last week cut a military hotline which was the last official direct link with Seoul - would risk full-blown conflict.
In Washington, President Barack Obama's spokesman that "despite the harsh rhetoric we are hearing from Pyongyang, we are not seeing changes to the North Korean military posture, such as large-scale mobilisations and positioning of forces".