North Korea has said it is ending its peace pact with South Korea following UN sanctions in response to their nuclear test last month.
Pyongyang vowed to shut its shared border and close its hotline with Seoul in response to the security council's unanimous vote to toughen sanctions for their third nuclear test. Monitors said it appeared twice as big as the previous test in 2009.
Before the vote the country warned of a pre-emptive strike against their "aggressors", threats reiterated after the sanctions, as they pledged to retaliate with "crushing strikes" to anyone who dared trespass onto their territory, adding they will cancel nuclear disarmament agreements with the South.
However South Korea's defence ministry said the North would become "extinct from the Earth by the will of mankind" if they carried out their threat. Experts pointed out Pyongyang had a history of such rhetoric and while he US said it was taking the threats seriously they added they were "not unusual."
Announcements that North Korea was cancelling the non-agression pact and shutting down the hotline came on state news agency KCNA.
The hotline was set up in 1971 to facilitate direct communication with the countries and is also used to co-ordinate trade and travel through the Demilitarised zone. It has been severed and re-opened several times since its inception.
Kim Jong-Un was also reported to have visited military units that shelled a South Korean island in 2010.
KCNA said he told soldiers they could be called upon to "annihilate the enemy" at any time.