A man accused of the gang rape and murder of a girl in northern India has been killed in police custody, an official said Thursday, sparking angry riots in the usually tranquil Himalayan region.

Hundreds of protesters furious over the police handling of the case chanted "we want justice" in the popular tourist hill resort of Shimla, with businesses remaining closed in some parts of Himachal Pradesh state.

There have been vigils and strikes across the region since the 16-year-old victim was found naked and mutilated in a forest, with many accusing police of bungling the investigation.

Tensions escalated further after a suspect held for the gruesome crime was killed in his cell by another inmate during a scuffle.

Nepalese national Suraj Singh, struck his head against the wall "and was taken to hospital where he was declared dead," said Z.H. Zaidi, the police inspector general.

News of his death triggered fury, with rioters torching a police station and vehicles.

The brutality of the crime shocked residents in Himachal Pradesh, a Himalayan state with some of India's lowest rates of sexual violence, and prompted calls for a swift investigation.

An autopsy confirmed the girl was gang raped and strangled. She sustained severe injuries in the assault, including a broken leg.

Six men were arrested but those calling for swift justice accused police of bungling the case, saying the main culprits were still at large.

"The main accused is roaming free. How can anyone die in police custody?" one protester in Shimla told Indian broadcaster NDTV on Thursday.

India has a gruesome record on rape. Nearly 40,000 rape cases are reported every year but the real number is thought to be much higher, with victims wary of how their complaints will be handled.

Nearly 2,200 rapes were registered in 2015 in the Indian capital New Delhi -- an average of six per day.

Himachal Pradesh recorded 244 rapes that same year, among the lowest rates in India.

source: AFP