North Korea shakes world with Hydrogen bomb test

North Korea said on Wednesday that it had carried out a successful miniaturised hydrogen bomb test, claiming a significant advance in its strike capability and setting off alarm bells in Japan and South Korea.

The test, which came just two days before North Korean leader Kim Jong-Un’s birthday, was initially detected as a 5.1-magnitude tremor at the main Punggye-ri nuclear test site in the north-east of the country.

The weapons yield was initially estimated at between 6 and 9 kilotonnes, similar to the North’s last nuclear test in 2013. The first US hydrogen bomb test in 1952 had a yield of 10 megatons.

“The republic’s first hydrogen bomb test has been successfully performed at 10:00 am (1:30 GMT),” North Korean state television announced.

The television showed Kim’s signed order–dated December 15–to go ahead with the test, with a handwritten exhortation to begin 2016 with the “thrilling sound of the first hydrogen bomb explosion.” “Let the world look up to the strong, self-reliant nuclear-armed state,” the handwritten note read.

The announcement triggered swift international condemnation, including from China and Russia, North Korea’s two main allies, but also scepticism, with experts suggesting the apparent yield was far too low for a thermonuclear device.

South Korean president Park Geun-Hye condemned what she described as a “grave provocation”. No countries were given advance warning of a nuclear test, South Korea’s intelligence service said. In previous such tests, Pyongyang had notified China, Russia and the US beforehand, they said.

Japan Prime Minister Shinzo Abe said: “North Korea’s nuclear test is a serious threat to our nation’s security and we absolutely cannot tolerate it.”

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.

“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  specialist Crispin Rovere.