Amnesty International is refused a presence in North Korea. But they do help point out the criminal level of abuse that happens there.
http://www.amnesty.org/en/region/north-korea
I think the problem you see is a refusal of the main-stream media to cover their reports, or the reports of others.
Actually, the problem I have with AA is their total lack of perspective.
Several years ago I researched AA’s annual report and found about 8 pages on North Korea and about 150 on the use of tasers in American prisons. Looking at such things, its obvious what their focus is.