North Korea 'declares war'

North Korea has declared 'a state of war' with South Korea in its most forceful threat against its neighbour amid heightened tensions in the region.

The reclusive communist state promised 'stern physical actions' against 'any provocative act' in a joint statement issued by the government, political parties and organisations.

It said it would deal with matters involving the south according to 'wartime regulations' and would retaliate to any threats without 'any prior notice'.

'From this time on, the North-South relations will be entering the state of war and all issues raised between the North and the South will be handled accordingly,' said the statement.

'The long-standing situation of the Korean peninsula being neither at peace nor at war is finally over.'

The increasingly harsh rhetoric and almost daily threats follows United Nations sanctions over Pyongyang's nuclear test on February 12.

Leader Kim Jong Un warned his forces are ready 'to settle accounts with the US' after two American B-2 bombers flew a training mission in South Korea.

North Korean state media later released a photo of Kim and his senior generals huddled in front of a map showing routes for envisioned strikes against cities on both American coasts.

The US National Security Council said it had 'seen reports of a new and unconstructive statement from North Korea'.

Analysts say a full-scale conflict is extremely unlikely and the North's threats are aimed at drawing Washington into talks that could result in boosting leader Jong Un's image at home.

The divided Korean Peninsula is already in a technical state of war because the 1950-53 Korean War ended in a ceasefire, not a peace treaty.

But Pyongyang said it was scrapping the war armistice earlier this month.