Images have been released revealing the scale of political prison camps in North Korea.
Amnesty International claims 200,000 people are being held in them in horrific conditions.
Amnesty says the images show four of the six camps occupying huge areas of land in wilderness sites in the provinces of South Pyongan, South Hamkyung and North Hamkyung.
Amnesty says there are signs that more people are being sent to the camps as North Korea clamps down on dissent before power is transferred to the son of the country's leader, Kim Jong-Il.
The BBC reports the North Korean government - which has previously denied the existence of mass political prison camps - has not publicly commented on the claims.
Amnesty says its report is also based on testimony from 15 former inmates and prison guards and a number of other people.
Former prisoners at one camp at Yodok said they were forced to work in conditions approaching slavery and were frequently subjected to torture and inhumane treatment.
Kim, a former prisoner in Kwanliso 15 at Yodok, says: Everyone in Kwanliso witnessed executions. All those who tried to escape were caught. They were interrogated for two to three months and then executed.''
