Seoul: In an audacious move by North Korea that is set to draw international concerns and flak, Pyongyang on Tuesday declared that it had successfully carried out the third nuclear test involving a miniaturised nuclear device.
North Korea added that the test was carried out in a "safe and perfect manner" at a northeastern nuke site.
North Korea`s official state media said the test is aimed at coping with "outrageous" US hostility that "violently" undermines the North`s peaceful, sovereign right to launch satellites.
The nuke test by Pyongyang is third since 2006, when the North had conducted its first ever nuclear test.
The second nuke test came in May 2009.
The move has drawn condemnation from around the world with the UN dubbing the test as "deplorable" and a "clear and grave violation" of the Security Council resolutions.
"It is deplorable that Pyongyang defied the strong and unequivocal call from the international community to refrain from any further provocative measures," said a UN statement issued by the Spokesperson for Secretary-General Ban Ki-moon.
US President Barack Obama , too, has come down heavily upon North, saying that the "provocative" nuclear test did not make North Korea more secure, quoted the BBC.
Obama further said that the US would remain vigilant and steadfast in its defence commitments to its allies in Asia. He also called for "swift" and "credible" international action in response.
North`s neighbour South Korea also condemned the nuclear test,saying "North Korea will not be able to avoid being held accountable for (the test)".
After the test, South Korea immediately heightened the military alert level to deter potential cross-border provocations following the North Korean test.
What sparked the nuke test fears was a tremor of magnitude 4.9 detected by the US Geological Survey in North Korea at a nuke site.
North Korea took three hours after the detection of the seismic activity to confirm that the quake was due to the nuclear test conducted there.
The earthquake was detected in North Korea`s Kilju county, North Hamkyung province, where a nuclear test site is located, said a news agency Yonhap.
South Korea`s defense ministry estimates the power of the blast at 6-7 Kiloton.
A South Korean Defence Ministry spokesman told reporters that the North had earlier informed China and the United States of its plans to conduct a nuclear test.
The North said it used a "lighter, miniaturized atomic bomb" that still has more explosive force than past tests. North Korea is estimated to have enough weaponized plutonium for four to eight bombs, according to American nuclear scientist Siegfried Hecker. However, it is not known whether North Korean scientists have found a way to miniaturize warheads.
Experts say regular tests are needed to perfect North Korea`s goal of building nuclear warheads small enough to be placed on long-range missiles.
This nuclear test would be seen as another big step toward North Korea`s goal of building a warhead that can be mounted on a missile.
It would also be a bold signal from young leader Kim Jong Un, who took power in December 2011 following the death of his father, Kim Jong Il.
The nuke test would also come as a challenge to the UN Security Council, which recently punished Pyongyang for launching a long-range rocket seen as a covert test of ballistic missile technology.
The United States and its allies have been on edge since North Korea said last month it will conduct its third nuclear test to protest toughened sanctions over a December rocket launch that the UN called a cover for a banned missile test.
North Korea`s powerful National Defense Commission said Jan 23 that the United States was its prime target for a nuclear test and long-range rocket launches. North Korea accuses Washington of leading the push to punish Pyongyang for its December rocket launch.
Earlier North Korea has carried out nuclear tests twice, in October 2006 and May 2009.
With Agency Inputs