Pyongyang said that having nuclear weapons was its right and condemned the council's vote on Saturday to impose sanctions, in a statement issued by the country's foreign ministry and carried by its official news agency.
The statement read: "The United Nations Security Council 'resolution'... cannot be construed otherwise than a declaration of a war against the DPRK [North Korea] because it was based on the scenario of the US, keen to destroy the socialist system.
"The DPRK wants peace, but is not afraid of war. It wants dialogue, but is always ready for confrontation."
North Korea also warned the US that if any nation used the UN resolution as a pretext for war, it would deal "merciless blows at him through strong actions".
It said it would be following US policy closely and would take unspecified "corresponding measures" accordingly.
The statement echoed comment's by Pak Gil Yon, North Korea's ambassador to the UN, who on Sunday accused the UN Security Council of "gangster-like" action and said that Pyongyang considered any further US pressure a "declaration of war".
On Tuesday, China urged North Korea not to increase tensions over the nuclear crisis and to enter into dialogue and consultation with other nations instead.
Liu Jianchao, a foreign ministry spokesman, said: "The important thing right now is that all parties concerned should refrain from taking any action that may further escalate the tensions."
Ivanov said Russia's reaction to
a second test would be negative
Meanwhile Mikhail Fradkov, Russia's prime minister, and Han Myeong-Sook, his South Korean counterpart, issued a joint statement on Tuesday saying that the test had posed a "grave threat" to the peace and stability of the region.
Russia and China are members of the six-nation forum which had been trying to negotiate an end to the North's nuclear programme, along with the two Koreas, Japan and the US.
Sergei Ivanov, Russia's defence minister, also warned that Russia's reaction to a possible second test "would be exactly the same as it was to the first nuclear explosion - that is, negative".
North Korea's announcement comes as Condoleezza Rice, the US secretary of state, is preparing to visit the region for diplomatic talks on implementing sanctions on the country.
Rice is expected to arrive in Japan on Wednesday before travelling to South Korea and China.
North Korea, one of the world's most isolated and secretive governments, faced global condemnation following its announcement of a successful nuclear test on October 9.
The US has since said that air samples taken in the region confirm the blast was nuclear.
The UN Security Council voted unanimously to impose sanctions targeting Pyongyang's weapons and missile programmes last Saturday.