The 73-page report, based on interviews with 203 Tibetan witnesses who had fled China and visitors who were in the Tibetan areas at the time, is the most comprehensive independent assessment so far of the mayhem two years ago. While the broad contours of the violence were known, many of the witness accounts and details of events in the report had not been documented before because foreign journalists were barred from the Tibetan areas. The authors said the report “finds that the scale of human rights violations related to suppressing the protests was far greater than previously believed, and that Chinese forces broke international law  including prohibitions against disproportionate use of force, torture and arbitrary detention, as well as the right to peaceful assembly  despite government claims to the contrary.”

“It also reveals that violations continue, including disappearances, wrongful convictions and imprisonment, persecution of families, and the targeting people suspected of sympathizing with the protest movement.”

Chinese officials have said the security forces exercised sufficient restraint and that Tibetans perpetrated the most heinous acts of violence.

At least 19 people were killed in the rioting that unfolded in and around Lhasa on March 14, 2008, when Tibetans burned and looted hundreds of stores run by Han and ethnic Hui merchants, the Chinese government said. Xinhua, the official Chinese news agency, reported in spring 2008 that more than 150 episodes of unrest took place from March 10 to March 28 in Tibetan areas. The government has blamed the Dalai Lama, the exiled spiritual leader of Tibet, for catalyzing the protests, although the Dalai Lama has denied any such role.

“In dealing with the incident, all related departments abided by the law and enforced it in a civil manner,” Qin Gang, a Foreign Ministry spokesman, said Thursday in a written statement responding to faxed questions about the report. “The accused are fully guaranteed the rights of litigation, and their ethnic customs as well as their dignity are respected.”