Chinese migrant workers have clashed with police for a third consecutive night outside the southern city of Guangzhou.
About 1,000 protesters set fire to cars and damaged government buildings on Sunday night near the city in China's manufacturing heartland, reports said.
Police reportedly fired tear gas and deployed armoured vehicles.
The protests began over the alleged mistreatment of a pregnant migrant worker by security guards.
Eyewitnesses said she fell to the ground - some say she was pushed - after a disagreement with security officials, who wanted her to move her stall from in front of a supermarket.
When news of the incident spread, other migrant workers - most from far-off Sichuan province - went on the rampage, says the BBC's Michael Bristow in Beijing.
Bricks and bottles were thrown at police, windows were smashed, and police vehicles were overturned, reports said.
At least 25 people have been arrested.
The town of Zengcheng - just outside Guangzhou - is a hub for clothing factories and is home to migrants working in a number of textile factories.
"The case was just an ordinary clash between street vendors and local public security people, but was used by a handful of people who wanted to cause trouble," Zengcheng Mayor Ye Niuping was quoted by the China Daily newspaper as saying.
Complaints about corruption and abuse of power are widespread, and incidents like this happen across China every week, our correspondent says.
The arrests follow a separate incident further north, in Lichuan city in Hubei province, where hundreds of people laid siege to local government offices following the death in custody of a respected local official.
The official, Ran Jinxian, had been arrested for allegedly taking bribes linked to land seizures and forced demolitions of people's homes.
Mr Ran, 49, was arrested on 26 May and died on 4 June. His family said he was beaten to death during interrogation.
Several officials have been detained or are under investigation over Mr Ran's death.