North Korea said it set off a hydrogen bomb Sunday in its sixth nuclear test, which judging by the earthquake it set off appeared to be its most powerful explosion yet.
South Korea's weather agency estimated the nuclear blast yield of the presumed test was between 50 and 60 kilotons, or five to six times stronger than North Korea's fifth test in September 2016. That would mark a significant step forward in the North's quest for a viable nuclear missile capable of striking anywhere in the United States.
On North Korean television, a newsreader called the test a "complete success" and said the "two-stage thermonuclear weapon" had "unprecedented" strength. Hours earlier, Pyongyang claimed its leader had inspected a hydrogen bomb meant for a new intercontinental ballistic missile.
Seoul's weather agency and the Joint Chiefs of Staff said an artificial 5.7 magnitude quake occurred at 12:29 p.m. local time, in Kilju, northern Hamgyong province, the site where North Korea has conducted nuclear tests in the past. Seoul officials revised their earlier estimate of 5.6 magnitude quake. The U.S. Geological Survey called the first quake an explosion with a magnitude 6.3.