North Korea on Sunday lashed out at South Korea's plan to launch a "preemptive strike" to thwart any nuclear attack from Pyongyang as "an open declaration of war," state media said.

The North's General Staff of the Korean People's Army warned the South Korean defence chief's recent remarks on a preemptive strike had created a "grave situation" which could lead to war "at any moment."

The North's armed forces "will take prompt and decisive military actions against any attempt of the South Korean puppet authorities... and blow up the major targets including the commanding centre," it said, according to the Korean Central News Agency.

The agency later carried a separate statement by the Committee for the Peaceful Reunification of Korea in protest at Seoul's alleged contingency plan for possible unrest in Pyongyang as well.

"This itself is a declaration of a war against (North Korea)," said the state committee which handles cross-border relations with the South.

The North's warning came days after the South's Defence Minister Kim Tae-Young reiterated that Seoul would launch a preemptive strike to frustrate any nuclear attacks by the communist regime.

"We would have to strike right away if we detected a clear intention to attack (South Korea) with nuclear weapons," Kim told a Seoul forum on Wednesday.

"It would be too late and the damage would be too big if, in the case of a North Korean nuclear attack, we had to cope with the attack."

The North's military statement said Sunday that its armed forces regard Kim's remarks as a "state policy" and "an open declaration of war" of Seoul.

Kim made similar remarks in 2008, sparking the North's angry protest and temporary expulsion of South Korean officials from a Seoul-funded industrial park just north of the heavily fortified border.

International efforts to bring Pyongyang back to six-party nuclear disarmament talks have so far made little headway.

North Korea abandoned the talks last April, a month before defiantly conducting a second atomic bomb test following its first in 2006, which soon led to United Nations sanctions on the communist state.

North Korea has said it will never return to talks with the United States, China, South Korea, Russia and Japan unless the sanctions are lifted. It also demands early discussions on a peace pact to end the 1950-1953 war.

But the United States and South Korea have insisted that the North should first come back to the talks and show it is serious about scrapping its atomic programmes.

US Assistant Secretary of State Kurt Campbell will visit Japan and South Korea early next month to discuss regional security issues including ways to revive the six-party talks last held in December 2008.

Seoul's Foreign Minister Yu Myung-Hwan said Friday he hopes the talks can resume "before or after the Lunar New year" holidays from February 13-15, but reaffirmed that sanctions will remain in force until progress is made.

Yang Moo-Jin, a professor of Seoul's University of North Korean Studies, told AFP Sunday Pyongyang is employing a "two-track approach" to Seoul.

"The North is employing a two-track approach, pressuring the South with vitriolic rhetoric on the political front while trying to cash in on cooperation on the economic front," Yang said.

The North has proposed holding one-day military talks on easing restrictions on travel in and out of the Seoul-funded estate just north of the border and two-day economic talks on reviving tours by South Koreans to the Mount Kumgang resort in the North from Tuesday.

Seoul has yet to respond to the offers. Both sides are due to resume separate non-military talks on the estate on February 1.