Geneva: UN high commissioner for human rights Navi Pillay on Friday urged China to promptly address the longstanding grievances of the Tibetans.
She said she was disturbed by "continuing allegations of violence against Tibetans seeking to exercise their fundamental human rights".
Pillay pointed to "reports of detentions and disappearances, of excessive use of force against peaceful demonstrators, and curbs on the cultural rights of Tibetans".
Cases have included a 17-year-old girl who was reportedly beaten and sentenced to three years in jail for distributing flyers calling for freedom and return of the Dalai Lama to Tibet.
Others have been sentenced to between four and seven years in prison for writing essays, making films or distributing photos of events in Tibet outside China.
Serious concerns have been raised about fair trial standards, and the torture and ill-treatment of detainees, the UN official said.
"I have had several exchanges with the Chinese government on these issues. But more needs to be done to protect human rights and prevent violations," Pillay said.
"I call on the government to respect the rights to peaceful assembly and expression, and to release all individuals detained for merely exercising these universal rights."
The high commissioner also appealed to Tibetans to refrain from resorting to extreme forms of protest, such as self-immolation, the UNHCHR said in a statement.
"I recognise Tibetans` intense sense of frustration and despair which has led them to resort to such extreme means," she said. "The government also needs to recognise this, and permit Tibetans to express their feelings without fear of retribution."