Police in southern China say they have arrested 25 people after clashes between residents and security forces near the city of Guangzhou.
A crowd threw bottles and bricks at police after a dispute between two street vendors and local security.
Riot police are also patrolling the city of Lichuan in central China after crowds attacked government offices.
Protests and clashes with police are common in China over corruption and land seizures by local officials.
In the Guangzhou incident, reports said people in the town of Xintang blocked traffic and damaged vehicles as the dispute between police and two street vendors, a migrant couple, escalated.
Police later seized control of the area, which is in southern China’s manufacturing heartland and is home to migrants working in a number of textile factories.
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.
“Ran’s cousin said he found signs of wounds and bruises on Ran’s body at the hospital and believed that they were signs of an ‘unnatural death’,” state-run Xinhua news agency said.
Residents of Lichuan said Mr Ran was arrested because he refused to co-operate with his superiors in a campaign of land requisitions.
Several officials have been detained or are under investigation over Mr Ran’s death.
There is widespread anger in China over corruption and the practice of seizing land and clearing out the residents to develop it for a profit.