The head of a special UN panel investigating allegations of massive human-rights violations in North Korea is calling for the government in Pyongyang to participate in the investigation.

Chairman Mike Kirby told a hearing Wednesday in Seoul he has sent the invitation to North Korean leader Kim Jong Un, but has not yet gotten a response. He says North Korea is welcome to participate or send observers to the hearings.

The five day meeting in the South Korean capital is hearing testimony from North Korean defectors about the conditions inside the prisons and labor camps run by Pyongyang.

There are an estimated 150,000 to 200,000 North Koreans living in prison camps. Defectors allege that many suffer beatings, torture, malnutrition. Executions are also common according to reports from defectors.

On Tuesday, Shin Dong Hyuk told the panel horrific stories about his life growing up in one of the North Korean labor camps.

"A guard asked her where she got the item in her pocket. She said she picked it up on her way (to school.) He was furious and said he didn't teach her to pick stuff off the road and started hitting her. She fell unconscious from the beating and the guard asked me to take her to her mother. The girl didn't come to school the next day and I heard she died. I think she was about 7 then."

Shin's life in the North Korean prison camp, including watching the execution of his mother and brother, has been detailed in a book called "Camp 14".