Tales of beatings, executions, starvation and forced labour have emerged from testimonies of former detainees at camps that North Korea denies even exist.
One such testimony comes from Kim Tae Jin, who spent four years inside camp 15 at Yoduk. Amnesty International estimates that 200,000 people live in the gulags.
Most are political prisoners, out of sight from the rest of the world. Others are born in the camps, knowing of little or no other life.
Al Jazeera's Emma Hayward reports from Paris, France.
Source: Al Jazeera