Human Rights Watch reported that Chinese forces fired indiscriminately on Tibetan protesters in 2008, beating others until they lay motionless.
The report cited eyewitnesses to the clashes, in which the government claimed it acted with restraint.
The Human Rights Watch report released Thursday gives a detailed examination — based on rare eyewitness accounts — of China's crackdown on the broadest anti-government uprising the country has faced from Tibetans in nearly 50 years.
Riots started in the Tibetan capital of Lhasa and then spread to communities across China's west.
Since the unrest, Beijing has sought to suppress accounts of rights abuses. It has flooded the region with troops, put Tibetans under tighter scrutiny, reduced the flow of international tourists and allowed in only a few foreign reporters under government escort.