Unmindful of international pressure, a defiant North Korea today conducted a second "successful" and "more powerful" nuclear test, a move that could invite fresh sanctions and punitive action against it.
The Korean Central News Agency said that the North "successfully conducted one more underground nuclear test on May 25 as part of the measures to bolster up its nuclear deterrent for self-defence in every way".
South Korea, Japan and Russia immediately condemned the test, calling it a development of "concern". The official news agency described the test as "more powerful" than the first one conducted on October 9, 2006, Kyodo reported from the North Korean capital.
The underground nuclear test follows a rocket launch last month, that prompted condemnation from the UN.
North Korea warned on April 29 that it would conduct a second test protesting the UN Security Council's rebuke for its April 5 rocket launch. The UN Security Council had imposed sanctions on North Korea and banned the country from all activities related to its nuclear weapons programme following its first test.
The KCNA report did not reveal the site of the test, but South Korea's Meteorological Administration detected an artificial earthquake of 4.5 magnitude this morning.Reports said the tremor was detected near Korean Central News Agency, the site where the first test was conducted.
The North said the second test was conducted "on a new higher level in terms of its explosive power and technology of its control." The results of the test "helped satisfactorily settle the scientific and technological problems... Further increasing the power of nuclear weapons and steadily developing nuclear technology," KCNA said.
South Korean President Lee Myung-bak called an emergency meeting of security ministers to study the test and discuss countermeasures, Yonhap news agency said.
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Meanwhile, Japan which announced the formation of a government crisis team, said it may try to get the UN Security Council to meet over the nuclear test.
"Japan will never tolerate North Korea's reported nuclear test and will take decisive measures," Chief Cabinet Secretary Takeo Kawamura said.
Russia reacted to the news, saying it was a matter of "concern" while EU external relations commissioner Benita Ferrero-Waldner said the test is "very, very worrying". US State Department spokesman, however, said Washington was unable to confirm a nuclear test "at this time".
The test threatens to jeopardise long-running disarmament talks involving China, Japan, Russia, South Korea and the US, to get North Korea to abandon its nuclear programme in return for energy aid and other benefits.
The six-party negotiations had led to a deal in 2007 under which the North had agreed to dismantle its nuclear facilities.