The latest test came just hours after North Korea said it now has advanced hydrogen-bomb capabilities, according to a report from the state-run Korean Central News Agency after the country’s leader Kim Jong-un visited a weapons facility in Pyongyang. Kim met with nuclear scientists and “watched an H-bomb to be loaded into new ICBM,” KCNA said.

North Korea first said it had tested a hydrogen bomb in January 2016, a claim that was met with skepticism. Hydrogen bombs are far more powerful than atomic bombs and the seismic pattern generated by the 2016 explosion wasn’t substantially larger than in North Korea’s previous nuclear tests. The January test was a 5.1 seismic event.

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