Defense Minister Itsunori Onodera said Wednesday that Japan now estimates a bomb North Korea tested Sunday had a yield of about 160 kilotons, based on a definitive analysis of the magnitude of the seismic activity observed during the detonation.

The Japanese government had initially put the yield at 70 kilotons, which is still far greater than the yields estimated in North Korea's five previous nuclear tests. It had later raised the estimate to 120 kilotons.

North Korea said the test was a detonation of a hydrogen bomb that can be mounted on an intercontinental ballistic missile, prompting the U.N. Security Council to convene an emergency meeting the following day.