An Indian court has sentenced three men to death for raping and killing a 20-year-old woman in a case that sparked massive protests against the state government of West Bengal and led to calls for greater safety for women.

Three other men involved in the attack in 2013 were sentenced to life imprisonment while two of the nine men charged were acquitted due to lack of evidence and one died in jail.

"We are happy with the verdict and sentencing," said the brother of the victim after the sentencing was announced by judge Sanchita Sarkar of the Bankshall Court in Kolkata on Saturday.

Public prosecutor Anindya Rout said that because of the brutality inflicted on the victim the death penalty was justified.


He said they would appeal the acquittal of two of the accused.

The rape and murder of the college student in Kamduni village in the eastern state of West Bengal was shocking in its brutality and reminiscent of the fatal gang rape of a 23-year-old woman on a moving bus in Delhi a year earlier.

That case turned a global spotlight on the treatment of women in India, where police say a rape is reported every 20 minutes.

India has since introduced tougher laws against sex crimes, and lowered the age at which someone can be tried for rape and other crimes to 16 years from 18.

But there has been no let-up in crimes against girls and women, with the number of rapes rising by 9 per cent in 2014 from the previous year to 33,707.

Rape victims in India have to contend with an archaic, poorly funded and insensitive criminal justice system and an often lengthy judicial process.

The West Bengal incident, in which the woman's throat was slit and her body dumped in a pond, led to the formation of a local activist group called the Kamduni Protibadi Mancha, which campaigned for quicker legal action.

The case was moved to the city sessions court in Kolkata after protests and alleged death threats to the accused and their lawyers.

Villagers calling for harsher penalties clashed with police outside the court during the trial.

Mausumi Koyal, who is a part of the Kamduni Protibadi Mancha, said the acquittal of two men was possible because of poor investigations by police and the Criminal Investigation Department.