The Korean Central News Agency
http://www.kcna.co.jp/index-e.htmThey host their site in Japan, because North Korea doesn't have the internet. News items usually are about lot's of wreathes laid at graves, flower basket gifts from other heads of states, announcements of upcoming military exercises of the aggressors (SK and US), and successes of the Juche ("self-reliance", we would say communist) philosophy of the state.
I didn't see any word of the nuk test on the website, which is interesting since everyone seems to be quoting the KCNA on it. Either the KCNA decided not to put it on their website, or they didn't say what they are being reported to have said. Make what you want out of that.
FYI: North Korea usually refers to itself as the Democratic People's Republic of Korea (DPRK), not North Korea. This is because there is no North or South Korea to them. There is one legitimate Korea, and that is the DPRK. South Korea is kind of like US occupied territory to them, or how the Southern states were viewed by the Northen States during the Civil War in the US.