"Probably wasn't a nuclear test."
North Korea (like Việt Nam), has fallen under the moniker of "Communist". The following shows how labels don't tell you much nowdays...North Korea Blast Created Mushroom Cloud, Yonhap Says (Update3) Sept. 12 (Bloomberg)
An explosion last week in North Korea created a mushroom cloud as wide as 4 kilometers, Yonhap News Agency reported, citing unidentified diplomats. A South Korean official said any blast probably wasn't a nuclear test.
This has also been reported in Channel News Asia. As for me: I'm glad this country isn't as scary as North Korea. All you have to worry about here is the killer traffic.
(Learnt via Steve Gilliards's aptly if not accurately named article Holy Shit, the North Koreans have a nuke.)