North Korea's worst concentration camp is a reeducation center where women who escaped to China are subjected to the most brutal treatment, NGO Good Friends said Monday.

The Jeungsan Reeducation Center in South Pyongan Province has a reputation for cruelty and the saying goes that even healthy people leave as cripples. The facility was turned into a reeducation center after the regime revised the criminal law in 2004.

Before the law was revised, North Korea had four kinds of detention centers -- reeducation, education, confinement and labor training camps in descending order of severity.

North Korean leader Kim Jong-il himself is said to have turned the center into a kind of "Papillon" prison island, giving instructions that every prisoner's year there should feel like 10.

The camp has since 1999 been used to detain female defectors. The North tightened controls for fear of regime collapse amid the famine of the 1990s, which sent many fleeing hunger and starvation. China regularly cooperated in the atrocity by sending refugees back to the North. Short of space at political camps, the regime started to put women in the Jeungsan camp.

Hundreds of female inmates reportedly suffer malnutrition there, and two or three die every day. Their bodies are wrapped in plastic and buried in mass graves. One former inmate who was detained there in 2004 said that other inmates who saw mass graves with piles of human bones and bodies came away with permanent psychological scars.

A former official of the Ministry of Public Security who defected said, "The Jeungsan Reeducation Center is notorious because many more inmates die there than at any other concentration camp due to the unbearably hard labor and malnutrition."

Jeungsan consists of 10 divisions, each of which is made up of seven to 10 groups. Each group normally has 40 to 50 inmates. A relatively healthy inmate is chosen as a capo who controls other inmates under the supervision of security guards. Those caught attempting to escape or committing infractions there are not publicly executed as at other political prison camps but are tortured or killed out of sight.