North Korea threatened a nuclear first strike Monday, ahead of planned spring manoeuvres by the United States and South Korea, according to dpa. In a statement through the state news agency, Pyongyang vowed a "preemptive and offensive nuclear strike" against the "undisguised nuclear war drills aimed to infringe upon the sovereignty" of North Korea. The regime fired several short-range rockets off its the eastern coast Thursday, hours after the UN Security Council imposed its strictest sanctions ever on Pyongyang, in response to the alleged test of a nuclear device in January and a long-range rocket test last month. North Korea issued similar threats three years ago ahead of the annual US-South Korean military exercises. Monday's statement said the "illegal and outrageous" sanctions make the country "boil like a crucible." The "indiscriminate nuclear strike" planned by North Korea would display the country's "military mettle."