The violence in the eastern city of Chizhou was the latest in a series of protests which the Communist Party fears could spin out of control, become a channel for anger over a growing gap between rich and poor, and threaten its monopoly on power.
State media quoting police on Wednesday said 10 people had been arrested in connection with the riot.
The official Xinhua news agency blamed Sunday's riot in Chizhou in dirt-poor Anhui province on a few criminals who led the "unwitting masses" astray.
A few men set on a teen they had hit with their car, a manager from a nearby supermarket, surnamed Wu, said.
The men were taken to a police station and a crowd that had been watching the fight swarmed around the building, Wu said, demanding that the men be handed over to them as their numbers swelled by the minute.
Some among the growing mob focussed their anger on the men's Toyota sedan, smashing it, flipping it over and setting it on fire, Wu added.
Later, three parked police cars received the same treatment by a crowd now several thousand strong.
Armed police tried to quell the disturbance, but were driven back by a hail of rocks and firecrackers, the store manager said. A local newspaper reported six policemen were injured.
"It was raining hard that day. Otherwise, more stores might have been looted"
Supermarket manager Wu
The crowd then crashed through the windows of Wu's store and began grabbing anything they could get their hands on.
By the time police arrived en force four hours later, the store had been stripped clean, Wu said.
"It was raining hard that day. Otherwise, more stores might have been looted," he added.
Armed police in full riot gear managed to restore order around midnight on Sunday, he said.
The riot followed a more violent incident in northern Hebei province earlier this month in which six villagers fighting to keep their land were killed and 48 injured in a skirmish with armed, hired thugs.