UNITED NATIONS — The U.N. Security Council responded swiftly to North Korea’s latest nuclear test by punishing the reclusive regime Thursday with tough, new sanctions targeting its economy and leadership, despite Pyongyang’s threat of a pre-emptive nuclear strike on the United States.

The penalties came in a unanimous resolution drafted by the U.S. along with China, which is North Korea’s main benefactor. Beijing said the focus now should be to “defuse the tensions” by restarting negotiations.

The resolution sent a powerful message to North Korea’s new young leader, Kim Jong Un, that the international community condemns his defiance of Security Council bans on nuclear and ballistic tests and is prepared to take even tougher action if he continues flouting international obligations.

“Taken together, these sanctions will bite, and bite hard,” U.S. Ambassador Susan Rice said. “They increase North Korea’s isolation and raise the cost to North Korea’s leaders of defying the international community.”

The new sanctions came in response to North Korea’s underground nuclear test on Feb. 12 and were the fourth set imposed by the U.N. since the country’s first test in 2006. They are aimed at reining in Pyongyang’s nuclear and missile development by requiring all countries to freeze financial transactions or services that could contribute to the programs.

North Korea kept up its warlike rhetoric Friday after the U.N. vote, issuing a statement saying it was canceling a hotline and a nonaggression pact with rival South Korea.

North Korea’s Committee for the Peaceful Reunification of Korea, the country’s arm for dealing with cross-border affairs with Seoul, said it will retaliate with “crushing strikes” if enemies intrude into its territory “even an inch and fire even a single shell.” It also said it was voiding past nuclear disarmament agreements between North and South Korea.

South and North Korea agreed in a 1992 joint declaration not to produce, test or use nuclear weapons. North Korea has since conducted three nuclear tests.

The resolution also targets North Korea’s ruling elite by banning all nations from exporting expensive jewelry, yachts, luxury automobiles and race cars to the North. It also imposes new travel sanctions that would require countries to expel agents working for sanctioned North Korean companies.

The success of the sanctions could depend on how well they are enforced by China, where most of the companies and banks that North Korea is believed to work with are based.

Tensions with North Korea have escalated since Pyongyang launched a rocket in December and conducted last month’s nuclear test — the first since Kim took charge. Many countries, especially in the region, had hoped he would steer the country toward engagement and resolution of the dispute over its nuclear and missile programs. Instead, the North has escalated its threats.

Immediately before the Security Council vote, a spokesman for Pyongyang’s Foreign Ministry said the North will exercise its right for “a pre-emptive nuclear attack to destroy the strongholds of the aggressors” because Washington is “set to light a fuse for a nuclear war.”

The statement was carried by the North’s official Korean Central News Agency.

In the capital of Pyongyang, Army Gen. Kang Pyo Yong told a crowd of tens of thousands that North Korea is ready to fire long-range nuclear-armed missiles at Washington, which “will be engulfed in a sea of fire.”

White House spokesman Jay Carney said the U.S. is “fully capable” of defending itself against a North Korea ballistic missile attack.

Experts doubt that the North has mastered how to mount a nuclear warhead on a ballistic missile capable of reaching the mainland United States.

The North Korean statement appeared to be the most specific open threat of a nuclear strike by any country against another. Sen. Robert Menendez, D-N.J., chairman of the Senate Foreign Relations Committee, called the threat “absurd” and suicidal.

North Korea also has threatened to scrap the cease-fire that ended the 1950-53 Korean War. It has a formidable array of artillery near enough to the Demilitarized Zone to strike South Korean and American forces with little warning.

The top U.S. envoy on North Korea, Glyn Davies, cautioned Pyongyang not to miscalculate, saying the U.S. will take necessary steps to defend itself and its allies, including South Korea, where it bases more than 28,000 U.S. forces.

“We take all North Korean threats seriously enough to ensure that we have the correct defense posture to deal with any contingencies that might arise,” Davies told reporters.

Rice said “the entire world stands united in our commitment to the denuclearization of the Korean peninsula and in our demand that North Korea comply with its international obligations.”

China’s U.N. Ambassador Li Baodong said the resolution reflects the determination of the international community to prevent nuclear proliferation, but he stressed that its adoption “is not enough.”

“The top priority now is to defuse the tensions, bring down heat ... bring the situation back on the track of diplomacy, on negotiations,” Li said.

The resolution stresses the Security Council’s commitment “to a peaceful, diplomatic and political solution” to North Korea’s nuclear program and urges a resumption of the long-stalled six-party talks involving both Koreas, the U.S., China, Russia and Japan.

South Korea’s U.N. Ambassador Kim Sook said North Korea’s threats and inflammatory statements will be dealt with “resolutely.”

“North Korea must wake up from its delusion of becoming a ... nuclear weapons state and make the right choice,” he said. “It can either take the right path toward a bright future and prosperity, or it can take a bad road toward further and deeper isolation and eventual self-destruction.”

Russia’s U.N. Ambassador Vitaly Churkin also warned that “new threats or trying to build up the military muscle in the region ... might be taking us away from the need to resume six-party talks,” which he added must be an international priority of all countries.

In addition to the sanctions, the resolution bans further ballistic missile launches, nuclear tests “or any other provocation,” and demands that North Korea return to the Nuclear Nonproliferation Treaty. It condemns all of North Korea’s ongoing nuclear activities, including its uranium enrichment.

It strengthens inspections of suspicious cargo heading to and from the country, calls on states to step up “vigilance” of possible illegal activity by North Korean diplomats.

To get around financial sanctions, North Koreans have been carrying around large suitcases filled with cash to move illicit funds. The resolution expresses concern that these bulk cash transfers may be used to evade sanctions. It clarifies that the freeze on financial transactions and services that could violate sanctions applies to all cash transfers as well as the cash couriers.

The resolution identifies three individuals, one corporation and one organization that will be added to the U.N. sanctions list. The targets include top officials at a company that is the country’s primary arms dealer and main exporter of ballistic missile-related equipment, and a national organization responsible for research and development of missiles and probably nuclear weapons.