BEIJING, Aug 30 (AFP) - The head of Tibet's prison system admitted Saturday that political inmates accounted for nine percent of the troubled Chinese region's total prison population.

Tsering Puncog, director of the Tibet Bureau of Prison Administration, said Tibet had only three prisons, where the number of inmates comprised 0.075 percent of the region's population.

Tibet's population officially stood at 2.4 million at the end of 1995, which would make the prison population around 1,800, according to Puncog's figures.

"Prisoners charged with endangering state security account for nine percent of that number. The rest have committed criminal offences," he was quoted as saying by the official Xinhua news agency.

The Chinese authorities usually deny the existence of any political prisoners, prefering to label all inmates as "criminals."

Puncog's remarks were contained in a general rebuttal to recent comments on Tibet by US Congressman Frank Wolf, who earlier this month accused China of gradually "swallowing" Tibet after returning from a trip he made to the Himalayan region disguised as a tourist.

"If Wolf had seen the prisons with his own eyes, and if he were not prejudiced, he would have found that our jails treat and reform prisoners with a spirit of socialist humanitarianism," Puncog said.

He also pledged that Tibet would throw open the doors of its prisons "to those who really want to know the situation."

The International Committee of the Red Cross (ICRC) has spent years negotiating prison access with the Chinese authorities.

Tibetans in exile and Western critics have charged China with implementing repressive policies that amount to cultural genocide in the Himalayan region.

Numerous reports of arbitrary arrest, torture and death in detention have been logged by human rights groups.