North Korea said Wednesday that it has successfully conducted its first hydrogen bomb test, which if true, would mean a dramatic escalation of the country's nuclear capability. The announcement came soon after South Korea reported a seismic event resembling an earthquake 30 miles from the Punggye-ri site where the North has conducted nuclear tests in the past.
South Korean officials and some experts questioned whether the explosion was indeed a full-fledged test of a hydrogen device. Speaking on condition of anonymity, a senior South Korean military official told NBC News that "we presume that it was not a hydrogen bomb test."
North Korean news agency KCNA reported that the country's leader, Kim Jong Un, "made the final decision on Jan. 3 to go ahead with the hydrogen test and accordingly we have conducted hydrogen bomb test at 10 a.m. on Jan. 6 with total success."
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North Korea held its last nuclear test in 2013. If Wednesday's claim is true, it will be the fourth nuclear test conducted by the country since it first tested a device in 2006, U.S. officials said.
The United Nations Secretary-General Ban Ki-moon condemned North Korea's announcement, calling it "profoundly destabilizing for regional security."