North Korea claims to have successfully tested its first hydrogen bomb, following reports of a large tremor recorded near the country’s main nuclear test site.

North Korean state media announced the test shortly after earthquake monitoring stations reported a 5.1 magnitude tremor near the Punggye-ri site.

The statement from Pyongyang said:

“Through the test conducted with indigenous wisdom, technology and efforts the DPRK fully proved that the technological specifications of the newly developed H-bomb for the purpose of test were accurate and scientifically verified the power of smaller H-bomb.

“The test means a higher stage of the DPRK’s development of nuclear force.

“By succeeding in the H-bomb test in the most perfect manner to be specially recorded in history the DPRK proudly joined the advanced ranks of nuclear weapons states possessed of even H-bomb and the Korean people came to demonstrate the spirit of the dignified nation equipped with the most powerful nuclear deterrent.”

The hydrogen bomb test would be the fourth nuclear test by North Korea since 2006.

Hydrogen bombs offer much greater power than the traditional atomic bombs like those dropped on Japan in 1945, as rather than being a straight fission reaction, they use a primary nuclear fission reaction to compress and ignite a secondary nuclear fusion reaction.

The US tested the world’s first hydrogen bomb in 1952 in the “Ivy Mike” nuclear test, with the Soviet Union and the UK following suit with similar designs in 1955 and 1957.