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 missiles.
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.
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.
President Trump responded to the tests with a series of tweets, in which he dubbed North Korea a "rogue nation" and said its "words and actions continue to be very hostile and dangerous to the United States."
"South Korea is finding, as I have told them, that their talk of appeasement with North Korea will not work, they only understand one thing!" Trump tweeted.
South Korea’s presidential office said the security chiefs for Seoul and Washington have spoken following North Korea’s sixth nuclear test. 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.
China’s foreign ministry released a statement saying “the Chinese government expresses its strong opposition and strongly condemns” the tests and urging North Korea to abide by the resolutions of the UN Security Council. Russia's Foreign Ministry also condemned the test.
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.
The recorded seismic event came hours after North Korea claimed it had developed a hydrogen bomb that could be mounted on its intercontinental ballistic missiles. viewing the alleged hydrogen bomb.
North Korea's state-news agency, the Korean Central News Agency, claimed the hydrogen bomb has ”great destructive power which can be detonated even at high altitude,” and that all the components of the hydrogen bomb were “homemade.”
Analysts said Sunday's test indicates that North Korea is getting close to posing a credible nuclear threat to the U.S.
"This looks like a major improvement in yield and the two-stage nature of the test supports the idea it was a test of a thermonuclear device," said Chad O’Carroll, CEO and founder of Seoul-based Korea Risk Group, a risk advisory firm specializing in North Korea.
“If, as North Korea says, the Hwasong-14 intercontinental ballistic missile can now be equipped with a thermonuclear device like the one tested today, it means the North is very close to being able to deploy credible battle-ready nuclear weapons that can target the U.S," O’Carroll added.
Last September, North Korea conducted its fifth nuclear test, showing its determination to be a nuclear-armed country despite ever tougher sanctions. The test drew a strong rebuke from ally China, which said it would protest the test with North Korea's ambassador in Beijing.
It flew a Hwasong-12 over northern Japan last week, the first such overflight by a missile capable of carrying nukes, in a launch Kim described as a “meaningful prelude” to containing Guam, the home of major U.S. military facilities, and more ballistic missile tests targeting the Pacific.
O’Carroll said that he expects North Korea to launch a new ICBM test soon, with a long-range trajectory of thousands of kilometers into the Pacific Ocean.
“If one or two more ICBMs can be tested successfully in this way, North Korea would then announce the battle-ready deployment of its ICBM force,” he said.