Shin Dong-hyuk told human rights investigators in Seoul his earliest memory of life in the camp were the public executions that inmates were forced to watch, The New York Times reported.
Shin, 31, said he witnessed a 7-year-old girl being clubbed to death for stealing a few grains of wheat while he had the tip of his finger chopped off for damaging a piece of sewing equipment.
"We were expendables they were keeping as beasts of labor, to get the most out of us before we died," he said.
Shin's account of life in a North Korean prison camp was delivered to a three-member Commission of Inquiry send by the United Nations Human Rights Council.
In March the panel was given a one-year mandate to investigate allegations of "systematic, widespread and grave violations of human rights," including possible crimes against humanity, by the North Korean authorities.
The panel began five days of public hearings Tuesday in a lecture hall at Yonsei University in Seoul.
They hope to interview 30 North Korean defectors.