MUMBAI: Days after the arrest of a lawmaker from India's ruling party in connection with the rape of a teenager, another case of the brutal rape and murder of a girl was reported on Sunday in the state of Gujarat in the country's west.

News of the incident followed days of protests by activists, who have accused authorities of failing to investigate attacks on women across the country. The protests have been driven in part by the BJP lawmaker's arrest last week for an alleged assault in the northern state of Uttar Pradesh, which the ruling Bharatiya Janata Party governs.

Sunday's reports concerned an incident that took place on April 5 in the western Gujarat city of Surat, the city's police commissioner, Satish Sharma, told Reuters.

"The body was recovered on April 6 by the side of a highway and according to a post mortem report, the girl was sexually assaulted and murdered on April 5," Sharma said. He added the victim -- who was 11, according to the post-mortem -- has not yet been identified and that police from Gujarat's neighbouring states have been asked to help trace her family.

"We have put our best teams in place with all senior police officials. To nab the criminals we first need to identify the body," Sharma said.

The post-mortem examination of the girl revealed a case of "strangulation and smothering" with 86 signs of minor injuries, including sexual assault, he said. Some of the injuries were old.

A separate case of gang rape and murder of an eight-year-old Muslim girl in the divided state of Jammu and Kashmir has also caused national anger as details emerged of how the girl was kidnapped, drugged and held in captivity as eight Hindu men assaulted her.

The crumpled body of the girl who belonged to a nomadic tribe that roams Kashmir's mountains was found in January but the case made slow progress until activists stepped up their campaign for an investigation.

The Surat incident took place in Prime Minister Narendra Modi's home state of Gujarat, where he was Chief Minister from 2001 until he took national office in 2014.

The weekend's protests, which echoed mass rallies against sexual violence in 2012, are piling pressure on Modi, who faces general elections due by May 2019, and he has promised to take action.

The United Nations is among the international bodies that condemned the two earlier incidents.

"We are deeply concerned about the prevalence of gender-based violence, including sexual violence against women and girls, which we are witnessing in India," Yuri Afanasiev, the UN resident coordinator in India, said in a statement last week.

Protest rallies are being staged all over India on Sunday, with Bollywood actors expected to participate.

India's opposition Congress party held a midnight candle-lit vigil at India Gate in New Delhi, the site where thousands of people protested in 2012 against a brutal gang-rape in the capital.

India registered about 40,000 rape cases in 2016, up from 25,000 in 2012, government data show. Rights activists say thousands more go unreported.