North Korea has detonated a hydrogen bomb with "perfect success", the secretive country's state media has announced.
It added that the device was designed to be mounted on its newly developed intercontinental ballistic missile.
Earlier, Japan confirmed its near neighbour had conducted a sixth nuclear test.
Japan's meteorological agency said the resulting tremors were at least 10 times as powerful as North Korea's previous nuclear test, last September.
Experts estimated that blast to have been around 10 kilotons.
It means this latest device was about five times larger than the bomb dropped on Nagasaki during World War II in August 1945.
N Korea blast 'five times bigger than Nagasaki'
http://news.sky.com/story/north-kore...fears-11018555