Thousands of residents have protested in the south-eastern city of Fuan after a road accident, smashing police cars and overturning three police vans.
The reason for the protest in Fujian province was unclear. Police said the incident was instigated by "a handful of lawless people". A resident said people became angry because police and ambulances took nearly an hour to arrive to help the injured, while a Hong Kong-based human rights group said it was to do with corruption.
Such protests have become increasingly common in China, and the violence on Saturday is another reminder that the new Communist Party leadership has to deal with underlying social discontent that often boils over.
People are fed up with corruption and high-handed officialdom, pensions that have not kept pace with inflation, and families being forced from their homes to make way for developments.