Hundreds of Chinese villagers were detained Monday after thousands of people took to the streets and set fire to police and government buildings in southwest China in protest over the handling of a teenage girl's death.

Police detained at least 300 people who allegedly participated in the riot, which began Saturday, in Weng'an, a county in Guizhou province, the Hong Kong-based Information Centre for Human Rights and Democracy said.

Some protesters were taken to detention centres, the human rights watchdog said.

Locals residents remained on the streets while police in riot gear patrolled the area, local television footage showed.

The unrest was sparked by allegations of a police cover-up to protect suspects. Family members of Li Shufeng believe the 16-year-old girl was raped and killed and that police didn't fully investigate. Police determined she committed suicide.

Citing relatives of the girl, the watchdog said Sunday that Li disappeared after being called away by three young men, two of whom were related to officials in the county's public security bureau.

The men were interrogated for a day and then released to the horror of the girl's family, the watchdog said.

Liu Zhongmin, a teacher at Li's school in Weng'an, said an initial investigation conducted by the county's medical expert determined that the girl had drowned.

Further investigations by higher level medical experts and authorities have not concluded, but residents fear the same conclusion will be reached, Liu said.

On Monday, crowds gathered for Li's funeral and others stood by a river where she was allegedly killed.

A note on her coffin read, "Killing people is not a crime: police are concealing," illustrating the crowd's disillusionment with authorities.

With files from the Associated Press