BEIJING  At least 1,000 rioters clashed with the police on Sunday in a regional capital in western China after days of rising tensions between Muslim Uighurs and Han Chinese, according to witnesses and photographs of the riot.

The rioting broke out Sunday afternoon in a large market area of Urumqi, the capital of the vast, restive desert region of Xinjiang, and lasted for several hours before riot police officers and paramilitary or military troops locked down the Uighur quarter of the city. The rioters threw stones at the police and set vehicles on fire, sending plumes of smoke into the sky, while police officers used fire hoses and batons to beat back rioters and detain Uighurs who appeared to be leading the protest, witnesses said.

At least 3 Han Chinese and one police officer were killed in the rioting and 20 were injured, according to Xinhua, the official news agency. Dozens of Uighur men were led into police stations with their hands behind their backs and shirts pulled over their heads, one witness said. Early Monday, the local government announced a curfew banning all traffic in the city until 8 p.m.

The riot was the largest ethnic clash in China since the Tibetan uprising of March 2008, and perhaps the biggest protest in Xinjiang in years. Like the Tibetan unrest, it highlighted the deep-seated frustrations felt by some ethnic minorities in western China over the policies of the Communist Party.