Five people have been killed in the latest protests in the city of Urumqi in western China.
The BBC says they were triggered by reports of a series of mysterious stabbings by people armed with hypodermic syringes.
Many of the protesters blame ethnic Uighur Muslims for the stabbings. Tear gas was used to disperse them.
It is unclear how the latest deaths happened.
Almost 200 people were killed in July in fighting between Muslim Uighurs and Han Chinese in the city, the capital of the Xinjiang region. It was the worst ethnic unrest in China for decades.
Authorities blame Uighur separatists, saying the violence was orchestrated by Uighur separatists in exile.