North Korea faced united global condemnation and calls for harsh sanctions yesterday after it announced it had detonated an atomic weapon in an underground test that thrust Pyongyang into the elite club of nuclear-armed nations.
The explosion prompted worldwide concern it could seriously destabilize the region. South Korea's spy chief said there were possible indications that Pyongyang was moving to conduct more tests.
The UN Security Council planned a meeting yesterday on the test, and the US and Japan were expected to press for more sanctions on the North.
US President George W. Bush called the North's reported nuclear test a provocative act that requires an immediate response from the Security Council.
Bush said he had spoken by phone to leaders of China, South Korea, Japan and Russia -- the other parties involved in long-stalled negotiations with North Korea -- and all agreed that the test was unacceptable.
Bush said US officials were working to confirm North Korea's claim that it detonated a nuclear device underground.
"Nonetheless, such a threat itself constitutes a threat to international peace and security. The United States condemns this provocative act," he said.
Bush said North Korea has been a leading proliferator of missile technology, including transfers to Iran and Syria, and warned Pyong-yang against a transfer of nuclear weapons.
"The transfer of nuclear weapons or material by North Korea to states or non-state entities would be considered a grave threat to the United States and we would hold North Korea fully accountable for consequences of such action," he said.
While stressing his commitment to diplomacy, Bush said he had told South Korea and Japan that "the United States will meet the full range of our deterrent and security commitments" in the Asia-Pacific region.
A US intelligence source said a preliminary examination of the data did not indicate a large blast, or a series of explosions, but stressed that analysts were still working on a a definitive evaluation.
It could take several days for intelligence analysts to determine whether the event was the result of an unsuccessful nuclear test, a small nuclear device or a non-nuclear explosion, said a US official who spoke on condition of anonymity.
"If it was a nuclear test, it appears to be more of a fizzle than a pop," the official said, calling it "a seismic event ... that would suggest an underground explosion."
South Korea said the blast was relatively small, while Russia said it had been perhaps as powerful as the nuclear bombs the US dropped on Japan during World War II.
"We have no doubt that it was a nuclear explosion," Russia's Defense Minister Sergei Ivanov said.
The North's official Korean Central News Agency said the underground test was performed successfully using the country's own technology and that no radiation leaked from the site.
The underground test "marks a historic event as it greatly encouraged and pleased the [Korean People's Army] and people that have wished to have powerful self-reliant defense capability," KCNA said in an English-language dispatch, adding that it was "a great leap forward in the building of a great prosperous powerful socialist nation."
If details of the test are confirmed, North Korea would be the ninth country known to have nuclear weapons.