Hundreds of riot police have taken up posts in a city in the southern Chinese province of Guangdong, seeking to establish order after three days of rioting triggered by the alleged mistreatment of a pregnant migrant worker by security officials.

The heavy police presence Monday in Zengcheng city follows a rampage late Sunday in which hundreds of protesters smashed windows and set fire to government buildings. Hong Kong television showed protesters overturning police cars and riot police firing tear gas at the demonstrators. The report said at least a dozen protesters were taken into custody.

Coverage of the unrest has been sparse in China's state-controlled media. But officials are quoted elsewhere as saying the riots began Friday evening with an altercation between police and a migrant street-vending couple who were reported blocking the entrance to a local supermarket. About 100 onlookers fought with police to prevent the couple from being taken away.

China's Global Times newspaper says more than 1,000 people gathered outside the town's police station the next night, attacking security personnel and damaging police cars.

The riots are the latest in a series of clashes between residents and authorities in various parts of China.

Last week, rioting erupted in a Guxiang township, after a migrant worker said to be seeking payment from a local factory for back wages came under attack by factory personnel.

Separately, thousands of people attacked government offices in the central city of Lichuan last week, following reports that a city councilor had been beaten to death by police.

In Inner Mongolia last month, thousands of locals mounted protests after a herder was killed by a truck driven by a Chinese coal mining employee. The driver was convicted of murder and sentenced to death last week.

In late April, Chinese truck drivers shut down some Shanghai port facilities to protest new fees and rising fuel prices they said were eating away at their profits.