North Korea successfully tests a hydrogen nuclear bomb.

North Korea has successfully tested a hydrogen bomb according to the country's state broadcast, making it the country's sixth nuclear test in the year. The warhead is for its intercontinental ballistic missile and Initial data suggests this is the most powerful weapon the country has ever tested.

KCNA, North Korea's official news agency, says the test was carried out to "examine and confirm" using the hydrogen bomb as a payload for an ICBM.  "It also marked a very significant occasion in attaining the final goal of completing the state nuclear force".

South Korea’s Joint Chiefs of Staff said in a statement that the South Korean military “detected a man-made earthquake near Punggye-ri and is analyzing whether it was a nuclear test. In response, our Korean military has raised its alert status and stepped up its surveillance on North Korea.”

The Japanese government also says the tremors detected in North Korea were a nuclear test.  “After analyzing data provided by the Japan Meteorological Agency, the Japanese government concluded that North Korea has conducted a nuclear test,” Japanese Foreign Minister Taro Kono said in a live television broadcast.