North Korea's official Korean Central News Agency claimed that it used a "smaller and lighter atomic bomb" in the test.
The North Korean bomb shell announcement came two hours and 40 minutes after the South Korean government said a 4.9-magnitude man-made quake was detected in Kilju, northeastern North Korea, around 11:57 a.m.
The Punggye-ri nuclear test site is located in Kilju, where nuclear tests were conducted in 2006 and 2009.
North Korea notified the United States, China and Russia of plans to carry out its third nuclear test on Feb. 11, a South Korean official said.
President Lee Myung-bak convened a National Security Council (NSC) meeting.
A South Korean diplomat in New York said the U.N. Security Council will meet at 9 a.m. (New York time) on Feb. 12, according to a news report.
reporter
Park Sae-jin
swatchsjp@ajunews.com