North Korea said Sunday it would never trade its nuclear weapons programme for aid and stressed its "unshakeable" stance to retain the deterrent, following a third atomic test last month.

The North's foreign ministry, in a statement carried by state TV, rejected suggestions that the impoverished state was using its weapons programme as a way of bullying neighbours into offering much-needed aid.

"The US is seriously mistaken if it thinks that the (North) had access to nukes as a bargaining chip to barter them for what it called economic reward," it said.

The comments came days after the US National Security Advisor Tom Donilon said Washington was willing to hold "authentic negotiations" with the North if it changed its behaviour.

"To get the assistance it desperately needs and the respect it claims it wants, North Korea will have to change course," he said last week.

But the North Sunday called its atomic weaponry a "treasured sword" to protect itself from what it called a hostile US policy.

The US "temptation" may work on other countries "but it sounds nonsensical" to the North, the foreign ministry statement said.

"The (North) would like to re-clarify its unshakeable principled stand on its nuclear deterrence for self-defence."

Last month's test, its most powerful to date, prompted the United Nations to further tighten sanctions imposed following previous nuclear tests and long-range rocket launches in 2006 and 2009.

The tougher sanctions, and an ongoing South Korean-US military exercise, sparked an angry response from Pyongyang, which said it was tearing up the armistice that ended the Korean War and ending non-aggression pacts with Seoul.

The country has suffered chronic food and fuel shortages for decades, with the situation exacerbated by floods, droughts, mismanagement and global sanctions.

International food aid, especially from South Korea and the US, has been drastically cut over the past several years amid tensions over the North's nuclear and missile programmes.

A six-nation aid-for-denuclearisation forum on the North, involving the two Koreas, China, Japan, the US and Russia, have been at a standstill since the last meeting in December 2008.

Almost 28 percent of the North's children aged under five are stunted from malnutrition, a 2012 UN national nutrition survey showed.

S. Korea border island calm despite N. Korea threat
Seoul (AFP) March 17, 2013 - Residents of a South Korean island closest to the tense sea border with North Korea have shrugged off a warning from Pyongyang urging them to flee ahead of "thunderous attacks", an official said Sunday.

The North's official website, Uriminzokkiri, told residents of five islands south of the border to leave, warning of "devastating consequences" if recent cross-border tension escalates into a full-scale conflict.

"The wisest choice when the fire of thunder rains down on you is running afar," it said in an editorial published late Friday.

It repeated criticism of an ongoing South Korea-US joint military drill, calling it a rehearsal for war that may prompt counter-attacks from the North.

"At a time like this... it will be the best for the residents at the five border islands like Baengnyeong and Yeonpyeong, the biggest flashpoint area between two Koreas... to evacuate as soon as possible," it said.

A North Korean artillery attack on Yeonpyeong island, in the Yellow Sea, in 2010 killed four South Koreans.

Young North Korean leader Kim Jong-Un recently threatened to "wipe out" the neighbouring island of Baengnyeong.

The latest threat however had caused little panic among the 5,000 residents of Baengnyeong, the closest island to the border, said an administrative official on the island.

"There's no visible sign of panic or mass exodus... people appeared to be accustomed to it to some degree," the official, who declined to be named, told AFP by telephone.

"They are less worried about the situation than people outside believe," she said, adding the authorities however had stocked up underground shelters and been holding daily drills to prepare in the event of a bombardment.

The disputed maritime border in the Yellow Sea has seen bloody naval clashes in the past and, with military tensions at their highest levels for years, is seen as the prime location for another confrontation.