Hours after an unusual seismic tremor was detected at the North's Punggye-ri nuclear test complex, Pyongyang's Korean Central News Agency (KCNA) said that the detonation was of a "high level" using a smaller device compared to its previous two nuclear tests, and that the test was carried out in a safe manner that did not affect the surrounding environment.
"The test was conducted in a safe and perfect way on a high level with the use of a smaller and light A-bomb unlike the previous ones, yet with great explosive power," the KCNA said in the English dispatch, adding that the test did not have any adverse effects on the surrounding environment.
"The specific features of the function and explosive power of the A-bomb and all other measurements fully tallied with the values of the design, physically demonstrating the good performance of the DPRK's (North Korea) nuclear deterrence that has become diversified."
Confirming a third nuclear test, South Korea's government issued a statement, saying the test violated past U.N. Security Council (UNSC) resolutions and posed an "unacceptable threat" to peace and stability in the region.
The nuclear test "is an unacceptable threat to peace and security on the Korean Peninsula and in the region and a head-on challenge to the international community," said the statement. "North Korea won't be able to avoid grave responsibility," it said, noting South Korea will try to take every possible measure to get North Korea to abandon its nuclear programs, including taking matter in the UNSC. The UN body is expected to convene an emergency meeting to discuss the latest provocation at 9:00 a.m. on Tuesday (New York time).
U.S. President Barack Obama also said Tuesday that North Korea's announcement of another nuclear test is a "highly provocative act" and pledged all necessary actions to defend his country and its allies.
In a statement released nearly four hours after the first report of North Korea's apparent nuclear test, Obama said the test violated the isolated communist nation's obligations under numerous United Nations Security Council resolutions.
Related to the latest provocation, South Korean Foreign Minister Kim Sung-hwan called his U.S. counterpart and pledged "swift and unified" action at the U.N. over North Korea's third nuclear test.
A ministry spokesman said Kim and U.S. Secretary of State John Kerry held talks by telephone and agreed to take action. He said South Korea has also been in "close consultations" with China.
An official at the Korea Meteorological Administration explains the artificial tremor caused by a nuclear detonation on Feb. 12, 2013. (Yonhap)
Seoul's Korea Meteorological Administration detected a magnitude 4.9 tremor at 11:57:50 a.m. with its epicenter located in Kilju County. The area, located in North Hamgyeong Province in the northeastern part of the communist country, is home to the North's Punggye-ri nuclear test complex that was used in the 2006 and 2009 nuclear tests. Other seismic detection agencies in other countries also picked up the artificial quake.
The North's KCNA said that the atomic weapon test is in response to the encroachment on the country's sovereignty following the launch of the Unha-3 rocket on Dec. 12. It said the test will bolster the country's defense against security threats from abroad. The report added that latest test will ensure peace and stability on the Korean Peninsula and in the surrounding region.
Pyongyang has been threatening since late last month that it will conduct a "high level" nuclear test after the U.N. Security Council condemned last year's rocket launch and warned the communist country not to engage in further provocations.
Despite claims that the test was a success, South Korea's defense ministry said the latest detonation resulted in a 6-7 kiloton atomic explosion that fell shy of a yield from a "boosted fission weapon" that some experts speculated the North wanted to test this time around. A kiloton is equal to 1,000 tons of conventional TNT explosive.
It said while the detonation resulted in a blast larger than the 1 kiloton device that Pyongyang used for its first test and the 2-6 kiloton weapon used in the second experiment, it was not as powerful as the 13 kiloton bomb dropped on Hiroshima by the United States at the end of World War II. An official said that judging by the overall yield as checked by seismic readings, the explosion was not "normal." Most nuclear experts said the 2006 test was a so-called incomplete detonation, with some even saying the 2009 test may have not resulted in the kind of explosion that Pyongyang wanted.
In addition, Seoul said it is keeping an eye out for further nuclear testing and the launch of another long-range rocket. South Korea has placed its military and police on a high level of readiness and said it is working closely with the United States military to bolster the country's intelligence gathering capability and deal with any threat.