"Local officials exercised restraint during the riot and repeatedly told the rioters to abide by the law," Xinhua quoted a local government official as saying.
"Police were forced to fire warning shots and put down the violence, since local officials and people were in great danger."
Xinhua gave few details of the incident, which took place in Garze county of Sichuan, but said that "rioters" had attacked the local township government office.
The incident was the latest in three weeks of unrest over Tibet that has angered and embarrassed China ahead of the Beijing Olympics in August.
China has blamed the Dalai Lama, the exiled Tibetan leader, for the protests and accused him of trying to sabotage the Olympics.
The Dalai Lama denies China's claims.
On Thursday, Lodi Gyari, an envoy for the spiritual leader, urged Beijing to cancel plans to run the Olympic torch relay through Tibet, saying to do so would be "provocative and insulting" given the unrest.
The protests began in Lhasa, Tibet's capital, to mark the anniversary of a failed 1959 uprising against Chinese rule of the Himalayan region.
Four days of peaceful protests erupted into rioting in Lhasa on March 14, and the unrest spread to other areas of western China with Tibetan populations, including Sichuan province.
China says Tibetan rioters have killed 18 civilians and two policemen. Before the latest unrest, Tibetan exiled leaders said 135-140 Tibetans had been killed in the Chinese crackdown.
China has ruled Tibet since 1951, after sending in troops to "liberate" the Buddhist region the previous year.