Now confirmed as a nuclear test, 6 - 7 kT. North Korean state media claims the device was "miniaturised", which analysts are saying equates to being small enough to be fitted as a warhead on a ballistic missile.
If you follow the trajectory of developments, it doesn't lead to a good place. Regime Change anyone? And remember what happened last time someone said that? Still, there may be no other option, given sanctions seem to do little to nothing to arrest NK's militaristic designs.
In case there was any doubt in which direction those designs are aimed:
http://www.abc.net.au/news/2013-02-0...attack/4502654