In its first government reaction since the UN Security Council imposed the measures, the Stalinist regime warned it would strike with "merciless blows" against any countries that impinged on its sovereignty.
The statement came as the United States sought to tighten the screws on the reclusive nation with a diplomatic drive aimed at cutting off its lifeblood by ensuring the UN measures are vigorously enforced.
Separately, China -- Pyongyang's closest ally -- promised to abide by the sanctions and urged North Korea not to escalate tensions.
"The important thing right now is that all parties concerned should refrain from taking any action that may further escalate the tensions," said Chinese foreign ministry spokesman Liu Jianchao.
Pyongyang dismissed the Council's unanimous decision as "immoral behaviour". It said having a nuclear weapon was its legitimate right and lashed out at the United States, which it accused of plotting to destroy the nation.
"The DPRK wants peace but is not afraid of war," the foreign ministry said, referring to the country's formal name, the Democratic People's Republic of Korea.
"We will watch US movements and take corresponding action," an unidentified spokesman said, quoted by the secretive regime's official KCNA agency.
"The UNSC 'resolution,' needless to say, cannot be construed otherwise than a declaration of a war against the DPRK because it was based on the scenario of the US, keen to destroy the socialist system."
Impoverished and almost completely isolated from the outside world, North Korea stunned the global community when it announced October 9 that it had conducted an atom bomb test.
After initial doubts, US intelligence officials confirmed it was a nuclear explosion but with an unusually low yield of less than one kiloton, suggesting it had at least partially failed.
Japanese Foreign Minister Taro Aso earlier Tuesday said Tokyo had received information of possible preparations for a second test after US spy satellites reportedly picked up suspicious movements of trucks and people near the blast site.
"I have received information on that, but can't disclose the details," Aso said. He did not elaborate, and other officials have cautioned there is little hard evidence to back up the reports.
Christopher Hill, the lead US negotiator on the North's nuclear programme, warned Pyongyang against a second nuclear test, as China and Japan also told the regime to stand down if it was considering such a move.
"I think we would all regard a second test as a very belligerent answer on North Korea's part to the international community," Hill said. "I think the international community will respond very clearly to the DPRK on this."
The US envoy, who was in Seoul as part of a swing through Asia to shore up enforcement of the sanctions, said the North must understand "that the international community is not going to accept the DPRK as a nuclear state.
The package of sanctions against the North is aimed at curbing the Pyongyang regime's nuclear and other weapons of mass destruction programmes.
Most controversially, it also allows for inspections of cargo going in and out of the country in an effort to prohibit any illicit trafficking -- actions which China and South Korea fear could provoke the regime.
Hill was in South Korea to lay the groundwork for US Secretary of State Condoleezza Rice, who arrives here Thursday on a haul that takes her first to Japan and later to China and Russia.
South Korea, which fears it will suffer dearly from any conflict, warned the sanctions must not push Pyongyang too far.
"Sanctions against the North should be carried out in a way to push North Korea back to the dialogue table," Prime Minister Han Myeong-Sook said. "They must not be implemented in any way that could spark an armed clash."
In Beijing, foreign ministry spokesman Liu said China would implement the sanctions while taking its own commercial interests into account.
"The Chinese side has always implemented the Security Council's resolutions seriously and in a responsible manner. This time is no exception," Liu said.
His comments came after the United States on Monday urged Beijing to honour its "responsibilities and obligations".
The White House's comments came amid specific concerns that Beijing might not carry out border inspections of cargo moving in and out of North Korea.
The inspections aim to prevent the cash-strapped North Korean regime from selling material for an atomic bomb to terrorists or rogue states.

Copyright AFP (Agence France-Presse), 2006