North Korea declares it is in a “state of war” with its neighbor the South, warning Seoul and Washington that any provocation would swiftly escalate into an all-out nuclear conflict.

North Korea declares it is in a “state of war” with its neighbor the South, warning Seoul and Washington that any provocation would swiftly escalate into an all-out nuclear conflict.

"As of now, inter-Korea relations enter a state of war and all matters between the two Koreas will be handled according to wartime protocol," the North said in a government statement carried by the Korean Central News Agency.

"The long-standing situation of the Korean peninsula being neither at peace nor at war is finally over," the statement said, adding that any US or South Korean provocation would trigger a nuclear war.

The North had announced earlier this month that it was ripping up the armistice and other bilateral peace pacts signed with Seoul in protest against South Korea-US joint military exercises.

The White House labelled the latest statement from Pyongyang as "unconstructive" and, while taking it "seriously", sought to place the immediate threat level in context.

"North Korea has a long history of bellicose rhetoric and threats and today's announcement follows that familiar pattern," said National Security Council spokeswoman Caitlin Hayden.

In Seoul, the Unification Ministry insisted the war threat was "not really new". The Defence Ministry vowed to "retaliate thoroughly" to any provocation, but added that no notable troop movement had been observed along the border.

RESPEONIBILITY, RESTRAINT
For its part, Russia called for "maxim responsibility and restraint" over the issue.

"We expect all sides to show maximum responsibility and restraint and that no-one will cross the line after which there will be no return," Grigory Logvinov, a Russian foreign ministry pointman on North Korea, told the Interfax news agency.