North Korea has threatened war with South Korea if Seoul "directly participates" in a tightening of sanctions by the United Nations.
Reuters wrote that the UN Security Council on Tuesday unanimously condemned North Korea's December rocket launch, expanding existing sanctions as punishment.
According to the Australian Associated Press, North Korea's Committee for Peaceful Reunification of Fatherland gave the following retort:
"Sanctions amount to a declaration of war against us. If the South Korean puppet regime of traitors directly participates in the so-called UN 'sanctions,' strong physical counter-measures would be taken."
The warning came a day after Pyongyang said it would target the US with a nuclear missile, and carry out a new nuclear test and more long-range rocket launches.
The fiery rhetoric came as even as China and the US moved to pressure Pyongyang into backing down on any planned nuclear test.
According to CNN, the English-language edition of the state-run Chinese newspaper Global Times wrote:
"China's role and position are clear when discussing North Korea issue in the UN Security Council. If North Korea engages in further nuclear tests, China will not hesitate to reduce its assistance to North Korea."
The US has already moved against Pyongyang indirectly, with economic sanctions on two North Korean bank officials and a Hong Kong trading company that it claims supports Kim Jong-un's proliferation of nuclear weapons.
Washington also spearheaded the UN resolution on stronger sanctions, supported by Japan and South Korea.
White House spokesman Jay Carney said on Thursday that North Korea's threat to target the US was "needlessly provocative."
According to the AAP, he said:
"Further provocations would only increase Pyongyang's isolation, and its continued focus on its nuclear and missile program is doing nothing to help the North Korean people."