North Korea has said it is entering a "state of war” with South Korea in the latest escalation of rhetoric against its neighbour and the US.A statement promised "stern physical actions” against "any provocative act”.North Korea has threatened attacks almost daily since it was sanctioned for a third nuclear test in February.However, few think the North would risk full-blown conflict. It has technically been at war with the South since 1953 as no peace treaty has been signed.An armistice at the end of the Korean War was never turned into a full treaty.‘Taking threats seriously’The North carried out its third nuclear test on 12 February, which led to the imposition of fresh sanctions.The annual US-South Korean military exercises have also taken place, angering Pyongyang further.A North Korean statement released on Saturday 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."The long-standing situation of the Korean peninsula being neither at peace nor at war is finally over.”In Washington, Caitlin Hayden, a spokeswoman for the National Security Council, said the US had "seen reports of a new and unconstructive statement from North Korea”. "We take these threats seriously and remain in close contact with our South Korean allies,” she said.Agencies