(CNN) -- Chinese police fired on hundreds of protesters this week in the Tibetan Autonomous Prefecture of Garze, killing eight people, the Tibetan Center for Human Rights and Democracy said Saturday.
Tibetan monks in exile read prayers during a protest in New Delhi, India, on Saturday.
China called the incident "a riot" and said an official was seriously injured.
The human rights center said that about 300 protesters -- monks and laypeople -- demonstrated Thursday to call for the release of two monks arrested earlier.
The monks were taken into custody after officials searched their residences, "looking for photos of the Dalai Lama."
As the group marched toward the county government headquarters about 8 p.m. in Garze, in southwestern Sichuan Province, they clashed with police, who fired into the crowd, the center said.
Dozens of people were injured, including three monks who were in "critical condition," the group said.
China's state-run news agency, Xinhua, reported that "rioters attacked the seat of the Donggu township government of Garze County."
An official with the prefectural government told Xinhua that "police were forced to fire warning shots and put down the violence, since local officials and people were in great danger."
"Local officials exercised restraint during the riot and repeatedly told the rioters to abide by the law," the news agency reported.
Beijing blames the Dalai Lama, the spiritual leader of Tibetan Buddhists who lives in exile in Dharamsala, India, and his followers for violence that erupted last month amid protests for Tibetan independence.
China has drawn international criticism for its crackdown on the demonstrations, which began peacefully last month on the 49th anniversary of a failed Tibetan uprising. See photos of the unrest »
The protests have thrown a shadow over the Olympic Games, set to take place in Beijing in August.
Tibet's self-proclaimed government-in-exile puts the death toll from those protests at about 140, but Chinese government restrictions make it difficult to confirm that number. Find out more about Tibet »
Chinese authorities have reported 19 people dead and say most of those killed were "innocent victims": Han Chinese targeted by Tibetans.
The fallout from the protests has caused a war of words between the Dalai Lama and China's leaders. E-mail to a friend