Pyongyang/Seoul/Washington, Feb 12 (IANS) Highly secretive North Korea said Tuesday that it has successfully conducted a third nuclear test to safeguard its national security against hostile American policy, a move that US President Barack Obama called highly provocative and prompted South Korea to put its military on high alert.
The nuclear test was carried out at 11.57 a.m. in North Korea's Kilju county, North Hamkyung province.
The world learnt of the nuclear test when an artificial earthquake with 4.9 magnitude was detected from the town where the North Korean nuclear test facility is located.
North Korea claimed the nuclear test was successful, Xinhua reported, citing the official KCNA news agency.
South Korea's military was immediately put on heightened alert to deter potential cross-border provocations, while the South Korean and US forces upgraded their border surveillance level.
North Korea conducted similar nuclear tests in 2006 and 2009.
President Obama said: "This is a highly provocative act that, following its December 12 ballistic missile launch, undermines regional stability, violates North Korea's obligations under numerous United Nations Security Council resolutions."
He said North Korea's latest move contravenes its commitments under the Sep 19, 2005, Joint Statement of the Six-Party Talks on North Korea's nuclear programmes and "increases the risk of proliferation".
Calling North Korea's nuclear weapons and ballistic missile programs as a threat to US national security and to international peace and security, Obama said the US "remains vigilant in the face of North Korean provocations and steadfast in our defense commitments to allies in the region".
Pyongyang vowed to proceed with missile and nuclear tests targeting the US, its "sworn enemy", after the UN Security Council adopted a resolution to condemn its Dec 12 rocket launch.
Japanese Prime Minister Shinzo Abe said the nuclear test conducted by North Korea was "regrettable".
The South Korean government called it a "clear violation" of UN resolutions.
"North Korea will not be able to avoid being held accountable for (the test)," National Security Adviser Chun Yung-Woo told reporters after an emergency security meeting presided over by President Lee Myung-bak.
A South Korean official said that North Korea had notified the US and China of its nuclear test plan a day earlier.
Neighbour China said it firmly opposes the latest nuclear test conducted by North Korea.
North Korea "conducted another nuclear test in disregard of the common opposition of the international community", said the Chinese foreign ministry, adding that "the Chinese government is firmly opposed to this act".
The foreign ministry said that it is the firm stand of the Chinese side to bring about denuclearisation of the Korean Peninsula, prevent nuclear proliferation, and safeguard peace and stability in Northeast Asia.
"We strongly urge (North Korea) to honour its commitment to denuclearisation and refrain from any move that may further worsen the situation...," said the statement.
It added: "The Chinese government calls on all parties to respond in a cool-headed manner and persist in resolving the issue of denuclearisation of the Peninsula through dialogue and consultation within the context of the Six-Party Talks."
The six-party talks, a negotiation mechanism that includes North Korea, South Korea, the US, China, Japan and Russia, were launched in 2003 but stalled in December 2008. North Korea quit the talks in April 2009.