Pyongyang described its first test of an atomic bomb as an "historic event" aimed at bettering peace and security. It comes just three days after a unanimous call from the UN Security Council for North Korea to abandon its nuclear testing programme.

China, an ally and benefactor of North Korea, called the test "brazen" and urged the country to return to talks aimed at getting it to abandon its nuclear programme in return for aid and security guarantees. North Korea has boycotted the talks, which Beijing has hosted, for almost a year in protest over US sanctions on its alleged illicit financial activities.

Russia demanded that North Korea take immediate steps to abandon its nuclear testing programme, but urged all nations to have restraint following the underground blast. A statement by the Foreign Ministry said the test was “fraught with danger for peace, security and stability in the region”. It said: “We demand that North Korea immediately undertakes steps to return to the nuclear non-proliferation regime and resume six-party talks."

South Korea, a key source of aid and investment in the North, said that it wanted the matter brought to the United Nations, where South Korean Foreign Minister Ban Ki Moon is due to be formally nominated as UN secretary-general later today. Roh Moo Hyun, the South Korean President, urged his countrymen to remain calm and said that his government will “sternly deal” with the development. “This is a grave threat to peace, not only on the Korean peninsula but in the region," he said.

Japan, which many analysts saw as most directly threatened by any North Korean nuclear test, said that it was considering options for further sanctions against Pyongyang and might push for a new UN resolution. “The prime minister’s office has been working on options for additional sanctions over the past two or three days,” Foreign Minister Taro Aso told reporters.

In a statement, Tony Blair condemned the test as a “completely irresponsible act” which showed their “disregard” for the concerns of the region and the wider world. He said: “This further act of defiance shows North Korea’s disregard for the concerns of its neighbours and the wider international community."

In a statement at the White House, President Bush said: "The United States condemns this provocative act. Once again, North Korea has defied the will of the international community and the international community will respond. This was confirmed this morning in conversations I had with leaders of China and South Korea, Russia and Japan. We reaffirmed our commitment to a nuclear-free Korean peninsula and all of us agreed that the proclaimed actions taken by North Korea are unacceptable and deserve an immediate response by the United Nations Security Council."

John Howard, the Australian Prime Minister said: "We are outraged that a country that has to rely on the international community to feed its own people, and to bring them back from the brink of starvation, devotes so many of its scarce resources to missiles and nuclear weapons progress."

The European Union presidency said the nuclear bomb test was a threat to regional stability and that it would work with the world’s major powers for a “decisive international response.”

President Putin said: "Russia certainly condemns the test conducted by North Korea. Enormous damage has been done to the process of nonproliferation of weapons of mass destruction in the world."

Shinzo Abe, the Prime Minister of Japan, told a press conference in Seoul: "A North Korea with nuclear weapons and ballistic missiles constitutes a grave threat. Japan will now consider harsh measures."

Jaap de Hoop Scheffer, the Nato Secretary-General, strongly condemned North Korea’s nuclear test and called an emergency meeting of the alliance’s ambassadors.

Helen Clark, the New Zealand Prime Minister, said: "North Korea should have no illusion of the gravity with which the international community views its action, Our major concern is the broader security concerns of a nuclearised Korean peninsular," she added.

Benita Ferrero-Waldner, the EU commissioner for external relations, described the test as unacceptable but said that there were no plans to cut humanitarian aid to North Korea.

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