The threat – in which North Korea referred to the sanctions as part of a “war of aggression” led by the United States – came from a spokesman for the North Korean Foreign Ministry immediately before the Security Council voted on the sanctions.

In a statement carried by North Korea’s official news agency, the spokesman said, “Since the United States is about to ignite a nuclear war, we will be exercising our right to pre-emptive nuclear attack against the headquarters of the aggressor in order to protect our supreme interest."

Such inflammatory rhetoric is not uncommon from North Korea, but Thursday’s comments were among the most specific threats of a nuclear strike by any country. A nuclear attack on the United States would be nothing short of suicidal, said the new chairman of the US Senate Foreign Relations Committee.

"I do not think the regime in Pyongyang wants to commit suicide, but that, as they must surely know, would be the result of any attack on the United States," said Sen. Bob Menendez on Thursday as the UN vote was underway.

“There should be no doubt about our determination, willingness, and capability to neutralize and counter any threat that North Korea may present,” he said.

While most US experts do not believe North Korea has the technological capacity to carry out a nuclear attack on Washington, State Department spokeswoman Victoria Nuland said the United States has no choice but the take such comments seriously.

“You have to take a government at its word when it makes these kinds of threats,” she said at a press briefing on Thursday.

“This kind of rhetoric is not surprising, it’s not new, and unfortunately this regime has regularly missed its opportunity to improve its relations with the outside world,” she added.

The UN sanctions were handed down unanimously by the Security Council in response to a third nuclear test by North Korea on February 12, a move that violated UN resolutions.

The sanctions will increase scrutiny of suspicious North Korean sea and air cargo shipments, make it tougher for North Korea to acquire materials for its weapons program, and clamp down on financial freedoms and luxury goods such as high-priced cars and yachts.

“These sanctions will bite and bite hard,” said Susan Rice, the US Ambassador to the UN.

Russia, which currently holds the UN Security Council’s presidency, issued a statement Thursday expressing hope that Pyongyang would take the new sanctions seriously and halt further nuclear and ballistic missile development.

“We expect that all sides involved in the regional affairs would not take any action that could aggravate the situation on the Korean Peninsula and in northeastern Asia,” the Russian Foreign Ministry said.

North Korean leaders are also upset with joint military training drills underway between the United States and South Korea, which they have suggested are tantamount to an “open declaration of war.”

"The US is massively deploying armed forces for aggression… under the smokescreen of 'annual drills'," said the North’s Foreign Ministry spokesman on Thursday.

Both the United States and South Korea have characterized the training drills as defensive in nature.