New satellite photos and witness testimony released by a top human rights group are revealing the extent of North Korea's vast and notorious system of prison camps.
Amnesty International's report Thursday detailed rape, murder and forced labor that allegedly takes place at the gulags, where as many as 200,000 people are held.
A former prison guard, who went only by the name Mr. Lee, worked at Camp 16 in the north of the country throughout most of the 1980s.
"The purpose of prison camps is to oppress, degrade, and violate the inmates for as long as they are alive."
Mr. Lee told Amnesty some detainees were forced to dig their own graves. They were then killed by being struck on the neck with a hammer.
Shin Dong-hyak, a former North Korean prison camp inmate who is now living in South Korea, agrees with Lee's assessment. "The political prison camps are for those who have committed grave crimes, worse than murderers. Once they are put into those camps, they are erased from all formal registry and they become non-existent. They live in a condition worse than animals. I cannot find a word that can describe their pains."
Camp 16 covers a sprawling 560 square kilometers, making it nearly the size of the South Korean capital, Seoul.
Amnesty says satellite photos from the last two years show new housing blocks at the camp. Evidence of mining and logging activity also suggested forced labor.
Kim Young-soon was detained from 1980 to 1989 at Camp 15, in the southern part of the country.
Watch related video by Henry Ridgwell for VOA
"There were two prisoners who were caught trying to escape and were publicly executed. In a public execution, the prisoner is first beaten half to death. He is tied to a pole up on a platform, with his hands tied behind his back. His feet are also tied, another rope is tied around his waist, and he is blindfolded. Then one guard shouts to the firing squad, 'In the name of the people, shoot the enemy of the revolution!' They shoot three shots to the head, three shots to the chest, and three to the legs. By then, the head drops and the body is dragged away."
Amnesty says it has shared its evidence of the prison camps with the United Nations Commission of Inquiry, which is looking into human rights abuses in the North.
North Korea has refused to work with the commission. It denies the existence of political prison camps.
This report was produced in collaboration with the VOA Korean service.