North Korea has threatened to turn South Korea into "debris" in a statement that demanded Seoul halt what the communist state called its policy of confrontation.
The statement was issued amid worsening relations between North and South Korea, with the North angry about anti-Pyongyang leaflets floated across the border by activists and defector groups based in the South.
Pyongyang has also complained about reports by South Korean media over the health of its leader Kim Jong-Il, who is said to have suffered a stroke.
The North's military threatened its neighbour with a pre-emptive strike, which it says would destroy everything.
It also says it would be a just war that would build an independent re-unified state.
Separately, Japanese Prime Minister Taro Aso says he has information that Mr Kim is probably in hospital, though still capable of making decisions.
The health of Mr Kim has been the subject of intense speculation since he failed to appear at a key anniversary parade in September.