TOKYO (Kyodo) -- Japan has raised its estimate of the explosive yield of North Korea's sixth nuclear test to 160 kilotons, 10 times the force of the atomic bomb dropped on Hiroshima in 1945, Defense Minister Itsunori Onodera said Wednesday.
"This is vastly greater than previous North Korean nuclear tests. We cannot rule out the possibility that this was a hydrogen bomb test," Onodera told reporters.
"(North Korea) is evolving not just their ballistic missiles but also their nuclear technology," he said.
Onodera said the new estimate is based on definitive seismic data from a commission promoting ratification of the Comprehensive Nuclear Test Ban Treaty.
The commission has informed Tokyo of its observation of magnitude-6.1 shaking during Sunday's nuclear test, up from provisional estimates of 5.8 and 6.0.
The 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 some 120 kilotons.
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