North Korea has conducted its fifth nuclear test.
The test which happened last week was more powerful than the Hiroshima bomb and a clear violation of United Nations resolutions.
The UN nuclear watchdog measured the bomb test, which created the equivalent of a 5.3 earthquake around the area.
The report on North Korean state television said the test was to measure the strength of its nuclear warhead.
The test now means that North Korea has mastered the ability to mount a warhead on a ballistic missile.
The country is currently banned by the United Nations from any tests of nuclear or missile technology.
But in recent months it has conducted a series of missile launches and has threatened to carry out nuclear attacks on its enemies.