Seoul, South Korea ? A former North Korean political prisoner Tuesday offered grim details of life in a communist regime prison camp, saying he saw many inmates die from overwork and starvation.

The ex-inmate, who survived the prison camp at Yodok, about 70 miles northwest of Pyongyang, said a former defector was beaten to death for having contacted Christian representatives in China, he said.

“Most people died of malnutrition and its complications,” said the inmate, who used the pseudonym Kim Chol-soo to protect relatives in the North from retaliation. Kim told a news conference that prisoners received a starvation ration of 21 ounces of food a day.

He gave reporters a list of inmates including 34 North Koreans who had tried to defect and 82 others including former senior bureaucrats, security officials and a diplomat. The identities of the prisoners could not be independently confirmed.

The North claims it doesn’t violate human rights despite widespread accusations of torture, public executions and other abuses. Between 150,000 and 200,000 people are believed to be held in its prison camps for political reasons, the State Department said in a report earlier this year.