The protest appeared to be in retaliation for the disappearance of a man who was in police custody in Qinghai province, the official Xinhua News Agency reported.

Six people were arrested for alleged involvement in the riot while another 89 people surrendered to police. All but two of them were monks, Xinhua said.

Several hundred people, including nearly 100 monks from the La'gyab Monastery attacked the police station of La'gyab, a township in the Tibetan prefecture of Golog, on Saturday, Xinhua said.

A man who answered the phone at Qinghai's public security department said he hadn't heard about the attack or the arrests. Phone calls to other police departments and government offices in the area rang unanswered Sunday.

The protesters also assaulted policemen and government staff, causing some slight injuries, the report said without elaborating. Police were searching for other monks who took part in the attack but had fled, Xinhua cited Ju Kezhong, a local official, as saying. Order has since been restored in the township, the report added.

The violence started after a man accused of supporting separatism escaped from police custody and went missing, Xinhua said. A Tibetan exile Web site says the man committed suicide after fleeing police.

Zhaxi Sangwu of Qinghai province had been under investigation for advocating Tibetan independence when he left a police station in La'gyab Saturday, prompting a manhunt. Xinhua cited authorities as saying the man fled after asking to go to the toilet and remained at large. It cited a witness as saying he was seen swimming in the Yellow River.

A report on what appeared to be the same incident by the Tibetan exile Web site phayul.com claimed the protest erupted because a man jumped into the Yellow River to commit suicide after escaping police while going to the toilet.

Phayul.com's report cited an anonymous source in Dharmsala, India, who was a former resident of the area, as saying the man was 28-year-old monk Tashi Sangpo. The source said police found a Tibetan national flag and political leaflets in his room.

Dharmsala is the seat of the Dalai Lama's self-proclaimed government-in-exile and the destination of many Tibetans who flee China.

The Web site's report said the monk's death sparked an anti-China protest in the township, with Tibetans out in the streets chanting Tibetan independence slogans. Security in Tibetan areas has been tightened in recent weeks as Beijing tried to head off trouble ahead of sensitive anniversaries this month.

March 14 marked the one-year anniversary of antigovernment riots in Lhasa, Tibet's regional capital, while March 17 marked 50 years since the Dalai Lama escaped into exile in India after Chinese troops crushed a Tibetan revolt.

So far, it appears that major demonstrations have been prevented. Small pockets of protests, however, have been reported by Tibetan rights groups in recent weeks. Most couldn't be independently confirmed because communication is spotty in those areas and residents who are reached usually won't talk for fear of official retaliation.

China claims Tibet has always been part of its territory, but many Tibetans say the Himalayan region was virtually independent for centuries and that Beijing's tight control is draining them of their culture and identity.