Tokyo - The Japanese government set up a crisis management office Monday after North Korea said it conducted its second nuclear test.

Prime Minister Taro Aso has also ordered ministers to gather information related to the nuclear test, as the Foreign Ministry said Japan confirmed seismic activity in Norht Korea.

The Japanese Meteorological Agency has also detected "artificial earthquakes," media reports said.

North Korea said it "successfully" conducted a nuclear test Monday, following up on earlier threats issued after the United Nations Security Council criticized a rocket launch by the Stalinist state. (dpa)