South Korea's president Lee Myung-bak orders his army officials to be alert over Pyongyang's warnings of a 'nuclear war' in the troubled peninsula, Press TV reported.
Lee's office said on Sunday that the president has summoned his top security officials, ordering them to "resolutely and squarely cope" with the North Korean threats.
"North Korea should give up its nuclear program ... and stop any kind of military threat," read a statement issued by the office. "We urge North Korea to respond in a sincere dialogue to improve South-North Korean relations."
The warning came after North Korea said on Saturday that it would continue to weaponize its used plutonium rods and to take "resolute military actions" against international efforts to isolate the country.
Earlier on Friday, the UN Security Council imposed tougher sanctions against the country over its most recent nuclear test. The sanctions include a wider ban on arms sales and the inspection of North Korean ships.
South Korean and American troops in the volatile peninsula are currently on high alert at the Yellow sea border.
Relations between the two Koreas deteriorated after the conservative government of President Lee came to power last year.
This is while a commentary in the North's state-run Rodong Sinmun newspaper on Sunday accused the US of planning a nuclear attack on Pyongyang, and warned that a nuclear war could break out on the Korean peninsula.
Pyongyang alleges that the US has 1,000 nuclear weapons stationed in South Korea, ready to be fired at North Korea -- a charge that Washington has denied.
The US already maintains a nuclear umbrella over South Korea. The security measure was taken after the Korean War ended in 1953.
Tension in the troubled Korean peninsula has built up since May 25, when Pyongyang staged it second nuclear test and fired a series of short-range missiles.