North Korea sharply escalated the rhetoric against its southern rival, claiming it would soon conduct "special actions" that would reduce South Korea's conservative government to ashes within minutes.
The threat comes amid concerns that North Korea may be plotting another provocation in the wake of an unsuccessful rocket launch condemned by the United Nations Security Council as a violation of a ban against missile activity.
UN secretary general Ban Ki-moon urged North Korea to refrain from "further provocative measures", telling reporters in New York today that such actions "will not be desirable for the peace and stability of the Korean peninsula".
North Korea characterised the April 13 rocket launch as a failed bid to send a satellite into space - not a disguised test of missile technology as Washington and Seoul claim. Two days after the attempt Pyongyang unveiled a new long-range missile at a military birthday parade for late President Kim Il Sung.
There are new concerns that North Korea may conduct a nuclear test as it did after rocket launches in 2006 and 2009. South Korean intelligence officials say recent satellite images show the North has been digging a new tunnel in what could be preparation for a third atomic test.
On the North Korean side of the Demilitarised Zone, a military guide said he believed his country needed atomic weapons to defend itself against the threat of attack from the US. "Nuclear weapons are not the monopoly of the United States," Lt Col Nam Dong Ho said. "It's my personal opinion, but I think we'll continue to conduct nuclear tests."
The military warned in a statement carried by the state-run Korean Central News Agency on Monday that it would launch "special actions" soon against the South Korean government and conservative media.
For days North Korea has railed against South Korean president Lee Myung-bak and conservative South Korean media for criticising its rocket launch and the celebrations of the centennial of Kim Il Sung's birth.
But the military message, attributed to the "special operation action group" of the Korean People's Army's Supreme Command, was unusual in its specificity. "Once the above-said special actions kick off, they will reduce all the rat-like groups and the bases for provocations to ashes in three or four minutes, in much shorter time, by unprecedented peculiar means and methods of our own style," it said.
The threat comes as North Korea's new commander in chief, Kim Jong Un, makes a show of support for the "military first" policy championed by his late father and predecessor, Kim Jong Il. North Korea is marking the 80th anniversary of the founding of its army.