Asia Pacific

North Korea conducts sixth nuclear test, says it has developed 'perfect' H-bomb

Japan confirms isolated nation's sixth nuclear test, says it will seek tougher U.N. sanctions

by Jesse Johnson, Reiji Yoshida and Tomohiro Osaki

Staff Writers

North Korea claimed Sunday to have successfully tested a hydrogen bomb capable of being loaded onto an intercontinental ballistic missile, presenting the U.S. and its allies with a new and more potent challenge as global condemnation poured in.

The test of the “two-stage thermonuclear weapon” — the North’s sixth atomic blast — was ordered by North Korean leader Kim Jong Un and was hailed as a “perfect success.”

“The H-bomb test was carried out to examine and confirm the accuracy and credibility of the power control technology and internal structural design newly introduced into manufacturing H-bomb to be placed at the payload of the ICBM,” the North’s Nuclear Weapons Institute said in a statement carried by the state-run Korean Central News Agency.

The credibility “of the operation of the nuclear warhead is fully guaranteed,” KCNA said. “It also marked a very significant occasion in attaining the final goal of completing the state nuclear force.”

The announcement of the test came just hours after Pyongyang claimed to have developed the weapon, with state-run media displaying pictures of its design.

There was no independent confirmation that the device detonated was in fact a hydrogen bomb.

The nuclear test was confirmed by the Japanese government, which said the North had conducted the blast, but criticism of the test was rife around the globe.

In Tokyo, Prime Minister Shinzo Abe slammed the test as “absolutely unacceptable” and vowed a tough response at the United Nations.

U.S. President Donald Trump, in his first response to a nuclear test under his administration, voiced concern over Twitter that Pyongyang had continued to flout the international community.

“North Korea has conducted a major Nuclear Test. Their words and actions continue to be very hostile and dangerous to the United States,” he tweeted.

Trump labeled the North “a rogue nation” and “a great threat and embarrassment to China,” which he said “is trying to help but with little success.”

Trump also appeared to invoke the specter of military action to rein in the North while also blasting Seoul’s calls for dialogue with their neighbor.

“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!” he wrote.

China, for its part, slammed what it called “wrong actions” by Pyongyang.

“We strongly urge the DPRK side to face the international community’s resolve on denuclearization of the peninsula, concretely comply with relevant resolutions of the Security Council, stop taking wrong actions that will deteriorate the situation and go against its own interests and come back to the track of resolving the problem through dialogue,” the country’s Foreign Ministry said, using the acronym for the North’s formal name, the Democratic People’s Republic of Korea.

Earlier Sunday, the Japanese government confirmed the test after two earthquakes resembling past underground explosions were detected near the North’s Punggye-ri nuclear test site.

“After examining the data we concluded that it was a nuclear test,” Foreign Minister Taro Kono said following an emergency meeting of the National Security Council.

Giving an idea of the blast’s power, the Meteorological Agency said later in the day that tremors caused by the test were “at least 10 times as powerful” as those generated by the atomic bomb Pyongyang detonated in September last year.

NORSAR, a Norwegian earthquake monitoring agency, estimated the yield at 120 kilotons — a figure significantly higher than the 15-kiloton “Little Boy” bomb dropped on Hiroshima and the 20-kiloton “Fat Man” dropped on Nagasaki at the end of World War II.

Chief Cabinet Secretary Yoshihide Suga, meanwhile, suggested that the test may have been of a hydrogen bomb, as the North claimed.

“Given the fact that the scale of tremor detected was the largest so far, we cannot rule of the possibility that it was a hydrogen bomb, although we are still conducting analysis,” Suga told a news conference Sunday evening.

Speaking earlier, Suga said the government had lodged a protest with Pyongyang through its embassy in Beijing and condemned the test in the “strongest language possible.” He said Tokyo will also call for the convening of an emergency session of the United Nations Security Council to discuss taking even stricter measures against the Kim regime.

South Korea also joined the chorus for tougher measures, with President Moon Jae-in vowing to push for “the most powerful sanctions” yet at the U.N. in a bid to completely isolate the communist state, the South’s Yonhap news agency reported.

Asked about the possibility of U.S. military action against the North, the Cabinet’s top spokesman reasserted that Tokyo’s position of ratcheting up pressure on the regime is what is most needed at the moment to change its policy and actions.

Pointedly, Suga didn’t rule out the possibility of Japan requesting a freeze on oil shipments to Pyongyang — an ultimate step that would soon paralyze the nation.

“We will consider multiple options from the perspective of what sort of sanctions would be most significant, by analyzing the country’s foreign currency revenues and its economic relationships,” he said. “And it’s true that (cutting off oil exports) is one of these options.”

Suga said the 6.1 magnitude quake — the biggest ever to result from a North Korean nuclear test — suggested the blast had generated “tremendous energy.”

He also urged the public not to panic, noting that after the five previous tests, the amount of radioactive substances spewed into the air was not enough to affect their daily lives.

For its part, the North said in the announcement that “there were neither emission through ground surface nor leakage of radioactive materials nor did it have any adverse impact on the surrounding ecological environment.”

China’s Nuclear Safety Administration, however, said later Sunday on its website that it had begun emergency monitoring for radiation along the border.

Prior to Sunday’s detonation, the blast carried out last September was the North’s “most powerful to date,” according to South Korea, which said it had a 10-kiloton yield.

In January last year, the North also claimed it had successfully tested a “miniaturized hydrogen bomb,” though experts cast doubt on that claim.

Earlier Sunday, the China Earthquake Administration and the United States Geological Survey estimated the initial quake occurred at around 12:30 p.m. in Japan, or noon in North Korea, at a depth of zero kilometers and with a magnitude of 6.3 near the North’s Punggye-ri nuclear test site. The two agencies also said a secondary event eight minutes later, likely a structural collapse, had registered as a 4.6 magnitude quake.

According to a report earlier Sunday, Kim had inspected the hydrogen device at the Nuclear Weapons Institute and watched the weapon being loaded onto an ICBM.

The hydrogen bomb, with “super explosive power,” was indigenously crafted and has an explosive yield “adjustable” to hundreds of kilotons, KCNA reported.

“The H-bomb, the explosive power of which is adjustable from tens kiloton to hundreds kiloton, is a multifunctional thermonuclear nuke with great destructive power which can be detonated even at high altitudes for super-powerful EMP attack according to strategic goals,” the report said, referring to the electromagnetic pulse that occurs when a nuclear bomb is detonated high in the atmosphere, producing damaging current and voltage surges that can disrupt electrical systems and devices.

The claims could not be independently verified, but pictures released by the North showed Kim in a black suit examining a metal, peanut-shaped casing — apparently a mock-up of the bomb itself. One photo showed what appeared to be the nose cone of a missile near the mock-up and another showed an apparent diagram of how the supposed bomb would fit onto the tip of the long-range missile.

Pyongyang conducted two successful ICBM tests in July — including one that experts say potentially puts Chicago and Los Angeles within range.

Still, despite its claims, questions remain over the North’s ability to mount a warhead on the tip of a missile that can survive the rigors of atmospheric re-entry.

Ahead of the test Sunday morning, Abe said after a telephone call with Trump that the two leaders had agreed to “further step up pressure” on Pyongyang, Abe told reporters after the 20-minute teleconference.

Abe didn’t directly mention Pyongyang’s H-bomb claim, saying only that the government would “calmly analyze” the situation, and it wasn’t clear if he was referring to the announcement.

“We completely agreed that we must thoroughly coordinate with each other and with South Korea, and cooperate closely with the international community, to increase pressure on North Korea and make it change its policies,” Abe told reporters at his official residence.

The call was the third between the two leaders since Tuesday, when the North fired an intermediate-range missile over Hokkaido and into the Pacific Ocean. It is extremely rare for the leaders of two countries to hold teleconferences so often, a scene that underlined the close personal ties Abe has forged with Trump.

“We have again analyzed the latest situation and discussed how we should respond,” Abe said. “We have completely agreed that we need to put more pressure on North Korea to make it change its policies.”

According to a senior Foreign Ministry official, Trump personally prefers to speak directly with Abe, rather than exchanging views through lower-level officials.

The U.S. leader’s preference has apparently resulted in frequent teleconferences with Abe, the official said.

Concerns in Tokyo over Pyongyang’s nuclear ambitions have surged to fresh highs since the launch over Hokkaido — the first unannounced firing over Japan of a missile designed to carry a nuclear payload.

North Korea’s continued provocations — including Tuesday’s overflight and a drill in March that Pyongyang said was practice for attacking U.S. military bases in Japan — have also worried Tokyo.

Both drills involved military units “tasked with striking the bases” of American forces, according to North Korean state media. Kim said the missile exercises would continue — possibly including more overflights of Japan.

Abe called Tuesday’s missile exercise an “unprecedented, grave and serious” threat, and Trump reiterated his stance that “all options” — an allusion to military action — remain on the table for reining in the isolated country.

North Korea says a credible nuclear deterrent is crucial to its survival, claiming it is under constant threat from a “hostile” U.S. Seven rounds of stinging U.N. Security Council sanctions over its nuclear and missile programs have failed to halt its atomic march.

Kim said the indigenous development of the hydrogen bomb had come at “a great price” but “expressed great satisfaction” over the claimed success.

“All components of the H-bomb were homemade and all the processes ranging from the production of weapons-grade nuclear materials to precision processing of components and their assembling were put on the Juche basis, thus enabling the country to produce powerful nuclear weapons as many as it wants,” he said.

“Juche,” or self-reliance, is the North’s homegrown go-it-alone ideology that is a mix of Marxism and extreme nationalism. It was widely preached by state founder Kim Il Sung, grandfather of the current ruler.

David Albright, president of the Institute for Science and International Security in Washington, said the statement and pictures “show that North Korea wants us to think it is working on thermonuclear weapons.”

But Albright said this was far from proven, noting that the pictures released looked “like a model in a room for models, not for loading nuclear devices into re-entry vehicles.”

Still, experts said the earlier announcement — in particular the comments on adjustable-yield weapons and EMPs — was likely to convey the direction of the isolated nation’s strategy for its atomic arsenal.

“The assertion that this warhead is variable-yield and capable of specialized weapons effects implies a complex nuclear strategy,” said Adam Mount, a senior fellow at the Center for American Progress in Washington.

“The statement implies that North Korea is considering limited nuclear strikes for escalation control — not just massive assured retaliation against an aggressor,” Mount said. “This suggests nuclear weapons could be used earlier in a conflict or in a wider range of circumstances.”