Kim Yong-chun said that military exercises conducted by South Korea near the border were a preparation for war with the North, and said that the North would use nuclear weapons in the case of conflict.

Relations between the two countries have been fraught since North Korea killed four South Korean citizens in their shelling attack on the Southern island of Yeonpyeong month, and the South's decision to conduct an extensive military drill involving tanks and fighter jets has heightened the tension.

The North had previously called the manoeuvres "warmongering" but this is the first time he has threatened the South with retaliation should they spill over into actual military action.

"The South Korean puppet forces perpetrated such grave military provocation as renewing their shelling against the DPRK [Democratic People's Republic of Korea] during their recent exercises for a war of aggression in the West Sea [Yellow Sea] of Korea," he said.

"This indicates that the enemy's scenario for aggression aimed at the start of another Korean War, has reached the phase of its implementation."

"The revolutionary armed forces of the DPRK are getting fully prepared to launch a sacred war of justice of Korean style based on the nuclear deterrent at anytime necessary to cope with the enemies' actions deliberately pushing the situation to the brink of a war," he added.

South Korean President Lee Myung-bak has promised immediate retaliation to any further Northern attack.