Footage of protests in Urumqi, Xinjiang, China, earlier today - originally uploaded to YouTube by user ufreeus with the following text:
China's Xinjiang hit by violence
The city of Urumqi in China's restive Xinjiang region has been hit by violence with cars burned and traffic blocked, Chinese state media says.
An unspecified number of people also attacked passers-by and damaged property, Xinhua news agency said.
Police had rushed to the area to maintain order, the agency said.
Xinjiang, in the far west of China, is home to about eight million Muslim Uighurs, some of whom want independence.
The Xinhua report did not say how many people were involved, or suggest a motive.
But an eyewitness told a Reuters source in Beijing that the rioters were Uighurs, numbering in their thousands.
Uighur activists in Japan and Germany said the same - and said that there had been arrests, AFP news agency said.
China enforces tight controls in Xinjiang and rejects calls from its Muslim Uighur people for self-rule.
The US state department accuses Beijing of human rights abuses in the region.
In a report released earlier this year, it said that "severe cultural and religious repression" of ethnic minorities in Xinjiang had increased.
Dissidents were being detained and harassed, and tight controls on freedom of speech and the internet were being maintained, it said.
Uighur separatists, meanwhile, have waged a low-level campaign against Chinese rule for decades and there are sporadic outbreaks of violence.
But campaigners accuse China of exaggerating the threat to justify tough security clampdowns in the region.