Leader Kim Jong-un is has escalated its diplomatic offensive against Seoul and Washington after coming under international sanctions for its nuclear test.
A statement carried by the North’s official KCNA news agency said: “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”.
However, the two Koreas have been technically in a state of war since their 1950-53 conflict ended with an armistice and not a peace treaty.
Thursday, the United States sent a pair of nuclear-capable B-2 bomber planes on a controversial run over the skies of South Korea, conducting what officials claim was a diplomatic sortie.
Officials said the aim was to reassure US allies South Korea and Japan in the face of recent threats from North Korea and to urge Pyongyang back to nuclear talks.
Kim Jong-un’s reaction, according to North Korean state media, was to order his country’s missiles ready to strike the United States and South Korea.
Russia has warned that heightened military activity near North Korea was falling into a “vicious cycle” that could get out of control.
Foreign Minister Sergei Lavrov has called on all sides “not to flex their military muscle” adding that Russia is “concerned that alongside the adequate, collective reaction of the UN Security Council, unilateral action is being taken around North Korea”.