e officials. Police contacted by telephone in Tibet declined to comment. Some 150 inmates in Tibet`s Drapchi Prison had flown the Tibetan flag and demonstrated within the compound`s walls on May 1, the Tibetan Centre for Human Rights and Democracy said in a statement sent to news agencies. The statement quoted a letter from an unidentified source in Tibet as saying that the Public Security Bureau (PSB) and the paramilitary People`s Armed Police (PAP) had been called in to quell the disturbance. "Armed police used every forcible means to clamp down on the demonstrators, leading to firing by the PSB and PAP armed forces on the unarmed political prisoners," it said. It was unclear whether any inmates had been killed or wounded, and police had arrested all those involved in the demonstration, it said. "Many are believed to have later been put in solitary confinement and to undergo brutal atrocities in those cells," it said, but gave no further details. Many Tibetans, accusing Beijing of trying to stamp out the region`s culture and its unique form of Buddhism, are opposed to Chinese rule and have agitated for more autonomy or even independence. Beijing has pointed to rising living and health standards as proof it has brought progress to the region since communist troops marched in in 1950. It also says historical evidence shows Tibet is a part of the Chinese empire. Tibet`s spiritual leader the Dalai Lama, who has lived in exile since an abortive 1959 uprising against communist rule, won the Nobel Peace Prize in 1989 for his non-violent campaign for more autonomy for his homeland.