According to reports from the U.S. Geological Survey, there was a small, 4.9 magnitude earthquake in North Korea late on Monday. The tremor's epicenter was reportedly near North Korea's previous nuclear test sites, where devices were detonated in 2006 and 2009, fueling rumors that the quake was the result of a nuclear explosion. Those rumors have now been confirmed by a United Nations Security Council diplomat, South Korea's Defense Ministry, who are reporting the test yielded an explosion of six to seven kilotons, and the North Korean government.

The Associated Press reports that a U.N. nuclear test monitoring organization initially called the tremor an "unusual seismic event."

"There is a high possibility that North Korea has conducted a nuclear test," said Chi Heoncheol, an earthquake specialist at the institute. Chi said a magnitude 3.9 magnitude earthquake and a magnitude 4.5 earthquake were detected in the North's 2006 and 2009 nuclear tests.

South Korean media quickly described the event as a "man-made earthquake," and the South Korean Defense Ministry raised its alert level.

Not long after the quake was reported, a United Nations Security Council diplomat said the seismic activity was due to a nuclear explosion.

UPDATE: South Korea's Yonhap News is reporting North Korea gave China advance notice of their plan to detonate a nuclear device earlier today.

UPDATE 2: CNN's Elise Labbott reports that U.S. officials were expecting such a test at "any moment."

UPDATE 3: The South Korean Defense Ministry said the test yielded an explosion of six to seven kilotons.

And according to Yonhap News, there will be an emergency U.N. Security Council meeting at 9 a.m. Tuesday morning.

UPDATE 4: South Korea has confirmed the nuclear test.

As has North Korea:

UPDATE 5: President Obama issued a statement condemning the attacks:

North Korea announced today that it conducted a third nuclear test. 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, contravenes its commitments under the September 19, 2005 Joint Statement of the Six-Party Talks, and increases the risk of proliferation. North Korea's nuclear weapons and ballistic missile programs constitute a threat to U.S. national security and to international peace and security. The United States remains vigilant in the face of North Korean provocations and steadfast in our defense commitments to allies in the region.

These provocations do not make North Korea more secure. Far from achieving its stated goal of becoming a strong and prosperous nation, North Korea has instead increasingly isolated and impoverished its people through its ill-advised pursuit of weapons of mass destruction and their means of delivery.

The danger posed by North Korea's threatening activities warrants further swift and credible action by the international community. The United States will also continue to take steps necessary to defend ourselves and our allies. We will strengthen close coordination with allies and partners and work with our Six-Party partners, the United Nations Security Council, and other UN member states to pursue firm action.

[Image via AP]