North Korea’s Kim Jong Un: says country has the H-bomb

International condemnation was swift today after North Korea said it had carried out a “successful” hydrogen bomb test, although the claim was greeted with simultaneous scepticism as a result of the seismic data generated.

Neighbours South Korea and Japan decried the pariah state gross violation of UN Security Council resolutions, while the White House said it was still studying the precise nature of the apparent test and vowed to “respond appropriately”.

“The republic’s first hydrogen bomb test has been successfully performed at 10:00 am (0330 GMT),” North Korean state television announced.

“With the perfect success of our historic H-bomb, we have joined the rank of advanced nuclear states,” it said, adding that the test was of a miniaturised device.

A hydrogen, or thermonuclear bomb, uses fusion in a chain reaction that results in a far more powerful explosion than the fission blast generated by uranium or plutonium alone.

Last month, North Korean leader Kim Jong-Un suggested Pyongyang had already developed a hydrogen bomb.

The claim was questioned by international experts and there was continued scepticism over Wednesday’s test announcement.

“The seismic data that’s been received indicates that the explosion is probably significantly below what one would expect from an H-bomb test,” said Australian nuclear policy and arms control specialist Crispin Rovere.

“So initially it seems to be that they’ve successfully conducted a nuclear test but unsuccessfully completed the second-stage hydrogen explosion,” Rovere said.

Bruce Bennett, a senior defence analyst with the Rand Corporation, was equally unconvinced.

“This weapon was probably the size of the US Hiroshima bomb but this was not a hydrogen bomb,” Bennett told the BBC.

“The bang they should have gotten would have been 10 times greater than what they got,” he added.

The test, which came just two days before Kim Jong-Un’s birthday, was initially detected by international seismology centres as a 5.1-magnitude tremor next to the North’s main Punggye-ri nuclear test site in the northeast of the country.

Whether an H-bomb or not, it was North Korea’s fourth nuclear test and marked a striking act of defiance that flew in the face of enemies and allies alike who have warned Pyongyang it would pay a steep price for moving forward with its nuclear weapons programme.

The three previous tests in 2006, 2009 and 2013 triggered waves of UN sanctions. Their failure to prevent a fourth detonation will place the Security Council under intense pressure to take more drastic action this time around.

White House National Security Council spokesman Ned Price said he could not confirm the H-bomb claim, but promised the US would “respond appropriately to any and all North Korean provocations”.

South Korea “strongly condemned” the test and warned Pyongyang that it would be made to “pay the price” for ignoring international opinion.