Experts cast doubt on claim, saying evidence points to test involving uranium or plutonium device, while UN security council will discuss possible sanctions

This article is more than 4 years old

This article is more than 4 years old

North Korea has conducted its fourth nuclear test, the country’s state media has announced, in a move that could take it a step closer to developing nuclear warheads capable of striking the US mainland.



Some experts, though, said initial evidence was pointing towards a test involving a uranium or plutonium device and not, as Pyongyang has claimed, a far more powerful hydrogen bomb.

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An announcement on North Korean television said the country had successfully tested a “miniaturised hydrogen bomb” underground on Wednesday morning, describing it as an “act of self-defence” against the US. North Korean claims about the size and type of bomb have not been independently verified.

If the claims are true, it would be the first time the North has successfully tested a hydrogen bomb and could also enable the secretive state to launch long-range nuclear missiles.

“If it’s true, it means they’ve made something smaller scale, capable of being put onto a missile, said John Carlson, the former head of the Australian Safeguards and Non-Proliferation Office. “I think we can assume the previous tests they’ve carried out have been devices too large to fit onto a missile.”

South Korea’s spy agency believes the seismic wave reported was more likely caused by an atomic bomb, Lee Cheol Woo, a South Korean politician, said.

Yang Uk, a senior research fellow at the Korea Defence and Security Forum, said: “Given the scale it is hard to believe this is a real hydrogen bomb. They could have tested some middle stage kind (of device) between an A-bomb and H-bomb, but unless they come up with any clear evidence, it is difficult to trust their claim.”

The North Korean state television broadcast said the test was a “complete success” which propelled the country into the “rank of advanced nuclear states”. It had been overseen by the country’s leader, Kim Jong-un and conducted ahead of his 33rd birthday this Friday.



“[North Korea’s] fate must not be protected by any forces, only by [North Korea] itself,” the broadcast said. North Korea would not abandon its nuclear weapons program as long as the US maintained what it called “its stance of aggression”.

“The US has gathered forces hostile to DPRK [Democratic People’s Republic of Korea] and raised a slanderous human rights issue to hinder DPRK’s improvement,” it said.

“It is just to have H-bomb as self-defence against the US having numerous and humongous nuclear weapons. The DPRK’s fate must not be protected by any forces but DPRK itself.”

The United Nations security council was planning to meet on Wednesday morning in New York to discuss North Korea’s nuclear test, council diplomats said.

The White House said it could not confirm North Korea’s claims, but added the United States would respond appropriately to provocations and defend its allies. The EU said the test was a “grave violation” of UN resolutions.

Phillip Hammond, the British foreign secretary, said on a visit to Beijing: “I think I can say that Britain and China are pretty much completely aligned on North Korean nuclear. We both strongly oppose the acquisition or testing of nuclear weapons by North Korea and we both want to see a resumption of the six party talks.

“So far as I think any of us can tell, there is no reason to doubt what the North Koreans are claiming – that they have carried out a test detonation of an H bomb. It is clearly very bad news for the non-proliferation agenda generally and for security in the region specifically.”

South Korean president Park Geun-hye said the country would take decisive measures against any additional provocations by North Korea and work with the international community to make sure the country pays the price for its latest nuclear test.

Park said the latest test could change the fundamental nature of the situation over North Korea’s nuclear programme.

Prime minister Shinzo Abe said Japan would make a firm response to North Korea’s challenge against nuclear non-proliferation, calling its test a threat to Japan’s security.



The test is bound to ratchet up tensions between the isolated country and its neighbours as well as Washington. China’s foreign ministry said that Beijing did not have advance knowledge of the test and added that it firmly opposes Pyongyang’s action.



North Korea conducted nuclear tests in 2006, 2009 and 2013, drawing condemnation and rounds of UN sanctions banning trade and financing activities that aid its weapons program.



A successful fourth test could deepen North Korea’s international isolation if the UN security council decided to respond with more sanctions. Pyongyang is thought to have developed several crude nuclear weapons.

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Since becoming North Korean leader in late 2011, Kim Jong-un has stepped up condemnation of joint US-South Korean military drills he believes are preparation for an invasion.



In early 2013, Kim responded to UN sanctions imposed after North Korea’s third nuclear test by unleashing a barrage of threats aimed at South Korea, the US and Japan.

Kim appears to have caught the world off-guard yet again. He did not mention his country’s pursuit of a nuclear deterrent in his New Year’s address, an omission some analysts say was designed to improve the prospects of a summit with the Chinese leader, Xi Jinping.

Last month Washington dismissed Kim’s claims that his country had developed a hydrogen bomb – a development that, if true, would mark significant progress in North Korea’s nuclear capability. Hydrogen bombs are capable of producing a far more powerful blast than basic atom bombs.

An intensity shake map released by the US Geological Survey on 5 January shows the location where a preliminary 5.1 magnitude earthquake struck in North Korea. Photograph: US Geological Survey/EPA

John Carlson said the veracity of North Korea’s claim would be difficult to determine “until we can analyse any gases emitted, and it could take several days for those to show up, if it all”.

He said it would be a “major challenge” for the North Korean regime to develop a thermonuclear weapon, particularly a miniaturised version, which required even greater expertise.

“Their claim would be far more convincing if it was a larger size,” he said.

Carlson, who headed Australia’s safeguards office for more than two decades, said it was possible Pyongyang had actually produced a lower-yield “boosted explosion”, in which the hydrogen isotope tritium undergoes partial fusion, allowing them to describe the device as a hydrogen bomb.

“I think it’s feasible that they’ve done that and they’re claiming that they’ve done more,” he said.

Speculation that the regime in Pyongyang had conducted a surprise nuclear test on Wednesday rose after seismologists from South Korea, China and other countries said they had detected a “manmade” earthquake in the country that could have been caused by an explosion.



South Korean meteorological officials said the epicentre of the quake was 49km (30 miles) from the Punggye-ri site in North Hamgyong province, where North Korea has conducted nuclear tests in the past.

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Yonhap news agency in South Korea said North Korea had not given notice of the test, which was carried out at 10am local time (1am GMT), to the US or its traditional ally China.

Wednesday’s tremor was a “suspected explosion”, the China earthquake network centre said on its website. It gave the magnitude as 4.9.

The US Geological Service said it had detected a 5.1 magnitude quake, and the European Mediterranean seismological centre said it had also detected unusual seismic activity in North Korea.

“We suspect a manmade earthquake and are analysing the scale and epicentre of the quake with the geoscience and mineral resource institute of South Korea,” a Korea meteorological administration official said in the South Korean capital, Seoul.