Police 'gunned down several rioters' on Monday in China's Xinjiang, in the worst street clash since two years in the remote northwest province bordering Central Asia.
At least four people including an armed policeman, a security guard and two hostages died in the gunfire after rioters reportedly stormed a police station in Hotan city at noon, set it ablaze, and took hostages.
"The police quickly converged on the scene and shot a number of rioters while freeing six hostages,'' reported Xinhua, China's official news agency.
An unknown number of injured were rushed to hospital.
Authorities did not immediately reveal the ethnic identities of the rioters.
The violence erupted days after the second anniversary of the July 2009 ethnic riots in Urumqi, the capital of Xinjiang, that killed about 200 residents and kept the restive province simmering under a severe security crackdown.
China's national counter-terrorism bureau was rushed on Monday to Xinjiang.
An activist made an unverified claim to Reuters that the police had opened fired on protestors and sparked the fight.
Longstanding tension divides Xinjiang's eight million Turkic-speaking, Muslim Uighur minority from the dominant influx of Han migrants.
Beijing has pumped funds to develop the oil-rich region on a goal of bringing its GDP on par with the national average in five years.
Discontented Uighurs complain that their cultural freedom is restrained and they claim that the region's economic policies mainly benefit the Hans.
Beijing has in the past blamed sporadic attacks in Xinjiang on fringe extremists seeking an independent Turkestan. Last year, seven paramilitary personnel died in a bomb attack in Xinjiang.