North Korea’s state-run broadcaster said on Sunday that the country had successfully conducted a test of a hydrogen bomb that can be loaded onto its new intercontinental ballistic missile.

The nuclear test was estimated to have a strength of 100 kilotons, according to South Korea's Yonhap News Agency, citing South Korean lawmaker Kim Young-woo, chief of the parliament’s defense committee. That yield would be roughly ten times more powerful than North Korea’s previous test in 2016 and would mark a significant step forward in the North’s quest for a viable nuclear missile capable of striking anywhere in the U.S.

President Donald Trump responded in a series of Sunday morning tweets writing, "North Korea has conducted a major Nuclear Test. Their words and actions continue to be very hostile and dangerous to the United States."

He also criticized Chinese and South Korean attempts to negotiate with North Korea.

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, Kim Jong Un, had inspected a hydrogen bomb meant for a new intercontinental ballistic missile.

According to a statement from South Korea’s Joint Chiefs of Staff, the quake is “presumed” to be the sixth nuclear test ever conducted by North Korea. The event caused the South Korean military to raise its alert level and put its nuclear crisis response team into action, according to Yonhap.

The office says U.S. National Security Adviser H.R. McMaster spoke with his South Korean counterpart, Chung Eui-yong, for 20 minutes in an emergency phone call about an hour after the detonation.

The Japanese government also confirmed that the tremors were caused by a nuclear test, Foreign Minister Taro Kono said in a press briefing after a meeting of Japan’s National Security Council. Japanese Prime Minister Shinzo Abe condemned the reported hydrogen bomb test on Sunday.

"It is absolutely unacceptable if North Korea did force another nuclear test, and we must protest strongly," Abe said, according to The Associated Press.

Data from the U.S. Geological Survey on Sunday showed that a magnitude 6.3 seismic event was detected in the North Hamgyeong Province. Later, the USGS said a 4.1 magnitude event was recorded eight minutes after the initial quake, "possibly a structural collapse" caused by the larger seismic event.

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