Well, the inevitable has happened. North Korea have tested a nuclear weapon.

BBC wrote:

North Korea says it has carried out its first test of a nuclear weapon. It said the underground test, carried out in defiance of international warnings, was a success and had not resulted in any leak of radiation. The US said intelligence had detected a seismic event at a suspected test site and Russia said was "100% certain" a nuclear test had occurred.

http://news.bbc.co.uk/2/hi/asia-pacific/6032525.stm