North Korea confirmed that it tested a hydrogen bomb earlier this morning, its sixth nuclear test since 2006, claiming the bomb to be its strongest yet.

The hydrogen bomb was designed to be mounted on a newly-developed intercontinental ballistic missile (ICBM), potentially allowing it to fly thousands of kilometers, putting parts of the United States at risk.

The test caused an earthquake with a magnitude of 5.7, which South Korea suspected to be a nuclear test conducted by North Korea.

North Korean television said that there would be an “important announcement” coming later today. The nature of the announcement was not revealed.

North Korea has previously conducted a military test by firing a missile at Japan a few days ago. The missile landed in the Pacific Ocean, 1,180km off the Japanese coast with no casualties or damages reported.

The BBC reports that the weapon appears to be the first powerful enough to carry a nuclear warhead.