SEOUL, South Korea (CNN) -- North Korea has conducted its second nuclear test, the country's state news agency announced Monday.
This screen grab from North Korean television on April 9 shows leader Kim Jong Il in Pyongyang.
The confirmation came little more than an hour after the U.S. Geological Survey reported a magnitude 4.7 seismic disturbance at the site of North Korea's first nuclear test in October 2006. The North Korea's Korean Central News Agency said Monday's test was conducted "as part of the measures to bolster up its nuclear deterrent for self-defense in every way."
In Seoul, South Korean President Lee Myung-Bak's office said the country was investigating the reported test and would hold an emergency meeting of its national security council.
And in Tokyo, Prime Minister Taro Aso's office said it has set up a special task force to look into the test and how to respond.
There was no immediate response from Washington or Beijing.
"The current nuclear test was safely conducted on a new higher level in terms of its explosive power and technology of its control and the results of the test helped satisfactorily settle the scientific and technological problems arising in further increasing the power of nuclear weapons and steadily developing nuclear technology," KCNA announced.
There was no immediate information on the yield of the weapon used. But the first North Korean test produced, according to U.S. intelligence estimates, an explosion equal to less than 1,000 tons of TNT -- a fraction of the size of the bombs the United States dropped on Japan at the end of World War II.