North Korea confirmed that it has "successfully" conducted its second nuclear test Monday, following a warning of retaliation it issued last month after the U.N.'s condemnation of its rocket launch.
"The Democratic People's Republic of Korea (North Korea) successfully conducted one more underground nuclear test on May 25 as part of measures to bolster its nuclear deterrent for self-defense," the official Korean Central News Agency was quoted as saying.
North Korea warned on April 29 that it would conduct the second test, following its first in October 2006, in protest against the U.N. Security Council's rebuke for its April 5 rocket launch.
Monday's report did not say where the test was conducted. The previous test occurred in Gilju, the country's northeast in North Hamgyong Province.
The North said the second test was conducted "on a new higher level in terms of its explosive power and technology of its control."
The results of the test "helped satisfactorily settle the scientific and technological problems," it said, "further increasing the power of nuclear weapons and steadily developing nuclear technology."
Seoul's Korea Meteorological Administration said it has detected an artificial earthquake at 9:54 a.m. with a 4.5 magnitude. In the previous test, the detected magnitude was 3.6, according to Yoo Yong-gu, an earthquaker detector at the agency.
South Korean President Lee Myung-bak called an emergency meeting of security ministers earlier in the morning to study the test and discuss countermeasures.