North Korea has confirmed that it has carried out its third nuclear test, after international monitors detected seismic activity close to the nation's nuclear test site.

The North Korean regime said it had "successfully" detonated a miniaturized nuclear device with "greater explosive force" in an underground test. "A third nuclear test has been successfully staged," the state-run Korean Central News agency said.

"The nuclear test was conducted as part of measures to protect our national security and sovereignty against the reckless hostility of the United States that violated our republic's right for a peaceful satellite launch," KCNA said.

The confirmation came after monitors in Seoul, Japan and the US detected an "artificial quake" at 11:57am Korean time. The South Korean Yonhap news agency said it measured 5.1 in magnitude and was located in Kilju county, where the Punggye-ri test site is located. The US Geological Survey measured it as a 4.9-magnitude quake at a very shallow depth of just 0.6 miles.

South Korea raised its military alert level after reports of a quake and the presidential office said that it was "likely" to be a nuclear test, according to Yonhap. Shortly later, a UN Security Council diplomat confirmed it was a nuclear test.

"We've been informed by the South Koreans that there's been a (North Korean) nuclear test," a UN Security Council diplomat told Reuters on condition of anonymity.

North Korea is not prone to seismic activity. It conducted nuclear tests in 2006 and 2009.

The reclusive and isolated state is banned under United Nations Security Council resolutions from developing nuclear and missile technology.

Confirmation of the test throws down a stark security and diplomatic challenge to US President Barack Obama at the start of his second term, and to regional neighbors China, Japan and South Korea, all of which have new or incoming leaders.

The UN Security Council has convened an emergency meeting to discuss the test later today. The first priority for the international community will be determining the precise nature and yield of any test and what it reveals about the technical level of the North's nuclear weapons program.

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 against 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 on January 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.

Last October, a spokesman from the commission told state media that the country had built a missile capable of striking the United States, but did not provide further details. A missile featured in an April 2012 military parade appeared to be an intercontinental ballistic missile, but its authenticity has not been verified by foreign experts.

READ FULL SOURCE ARTICLE: 02/12/2013