The latest outburst of belligerence came as North Korea's main ally China warned that it could pull its aid if North Korea doesn't tone it down and drop plans for another nuclear test.
North Korea warned of "strong physical counter-measures" against South Korea if the country takes a "direct part" in U.S.-backed sanctions recently passed at the U.N.
The statement was released by North Korea's Peaceful Committee for Reunification with the Fatherland. It came a day after another bellicose statement warning of imminent rocket launches and a third nuclear test targeting the U.S. Those remarks were issued by the National Defense Commission, which is headed up by North Korea's new leader, Kim Jong-Un.
China has long been North Korea's main supporter in the region and a key provider of energy and food aid.
China signaled its frustration with North Korea in an op-ed in the ultra-nationalistic newspaper the Global Times. "If North Korea engages in further nuclear tests, China will not hesitate to reduce its assistance to North Korea," the editorial said. it went on to say that if the U.S., Japan and South Korea "promote extreme U.N. sanctions on North Korea China will resolutely stop them and force them to amend these draft resolutions."
China supported tightening sanctions against North Korea after its December missile launch.
That launch was considered North Korea's most successful to date. Observers say debris analyzed after the launch indicate North Korea is attempting to develop technology needed to mount a nuclear warhead on a missile capable of reaching Hawaii and, with time and development, the continental U.S.
Now, with the possibility of a third nuclear test on the horizon, China reminded North Korea of what is at stake.
North Korea's warnings also come as Sen. John Kerry prepares to take over from Hilary Clinton as Secretary of State. In Washington D.C. on Thursday Kerry spoke of an increased dialogue between the U.S. and China and the possibility for improved communication with North Korea. That looks unlikely given North Korea's indication it has turned its back on ever returning to six-party talks.
American intelligence of the Punggye test site in northeastern North Korea indicates preparative activity is underway. Because the test site is underground, spy satellite data is not a reliable predictor of exactly when a test could take place. North Korea's previous tests came at varying intervals after public threats were made. In 2006, its nuclear test fizzled out. A second test soon after President Obama took office was considered mildly more successful.