North Korea threatened to retaliate against South Korea for taking it to the UN Security Council over the sinking of a warship, calling the action an "intolerable provocation".
South Korea officially asked the UN Security Council on Friday to punish North Korea, accusing its nuclear-armed communist neighbour of blowing apart one of its warships with a torpedo, killing 46 sailors.
It was the first time Seoul has taken Pyongyang to the Security Council for an inter-Korean provocation, despite a history of being attacked by the North.
North Korea - which denies involvement in the sinking - issued a statement saying the South's action will intensify military tension and could trigger a war on the divided peninsula.
"That is yet another intolerable provocation to us," the North's Committee for the Peaceful Reunification said.
The statement - carried by the official Korean Central News Agency - was Pyongyang's first response to Seoul's request for UN action over the March 26 sinking.
The North Korean committee said its military will launch a "stern punishment" against South Korea if it does not halt anti-North Korea steps. It did not elaborate on what action it might take.
The Security Council has several choices: a resolution with or without new sanctions against North Korea, a weaker presidential statement calling for specific actions, or a press statement.
The Security Council earlier imposed sanctions against North Korea after its two nuclear tests in 2006 and 2009. These include UN embargoes on nuclear and ballistic missile-related items and technology, on arms exports and imports except light weapons, and on luxury goods.
UN diplomats familiar with consultations on possible action against North Korea said China, the North's closest ally, is opposed to new sanctions and indicated the more likely result will be a presidential statement.