North Korea says it successfully conducts nuclear test Yonhap / EPA The leadership of the Bank of Korea in Seoul, South Korea, Feb. 12, holds an emergency meeting on to check the financial market in the wake of North Korea's reported nuclear test. Earlier in the day, seismic activity was detected in North Korea's northeastern county of Kilju, which was believed to be the result of the North's third nuclear test. By Jack Kim, David Chance and Louis Charbonneau, Reuters Updated at 1:07 a.m. ET: SEOUL - North Korea confirmed on Tuesday it has successfully conducted a third nuclear test, saying it used a miniaturized device that had a greater explosive force than previous tests, the North's KCNA official news agency said. "It was confirmed that the nuclear test that was carried out at a high level in a safe and perfect manner using a miniaturized and lighter nuclear device with greater explosive force than previously did not pose any negative impact on the surrounding ecological environment," KCNA said. Seismic activity measuring 4.9 magnitude was registered by the U.S. Geological Survey. The epicenter of the seismic activity, which was only one kilometer below the Earth's surface, was close to the North's known nuclear test site. "We've been informed by the South Koreans that there's been a (North Korean) nuclear test," a U.N. Security Council diplomat told Reuters on condition of anonymity. An international nuclear test monitoring agency said the location of the seismic event was "roughly congruent with" 2006 and 2008 tests carried out by the reclusive state and had "clear explosion-like characteristics." North Korea, which had been threatening a third nuclear test, had informed Beijing and Washington on Monday of plans to undertake a test, South Korea's Yonhap news agency reported. The isolated state, which is banned under U.N. Security Council resolutions from developing nuclear and missile technology, did not make any immediate comment. North Korea is not prone to seismic activity and it may take hours or even days to determine officially whether a nuclear test had been conducted. South Korea's defense ministry said the North Korean seismic event could be the result of a 6-7 kiloton or stronger nuclear blast. South Korea's President Lee Myung-bak called a national security council meeting for 0400 GMT. North Korea successfully launched a long-range rocket in December in violation of U.N. resolutions that banned it from developing missile or nuclear technology after nuclear tests in 2006 and 2009. Toru Hanai / Reuters Japan Meteorological Agency's earthquake and tsunami observations division director Akira Nagai points at a graph of ground motion waveform data observed in the morning in Japan during a news conference in Tokyo Feb. 12. Seismic activities detected in North Korea may be the result of a nuclear test, Japan's top government spokesman said. It announced plans for a third nuclear test in response to the sanctions imposed in January after the rocket launch, although satellite imagery indicated it has been readying its test site for more than a year. The U.N. Security Council will hold an emergency meeting on North Korea's apparent nuclear test at 9:00 a.m. EST on Tuesday, council diplomats said. Diplomats had said previously that the United States, South Korea and European members would want the Security Council to adopt a resolution that would impose new sanctions on Pyongyang in the event of a third nuclear test in defiance of earlier council resolutions. Getting approval on a council resolution, however, could take weeks.