Indian rights groups voiced dismay Saturday over death sentences handed to four men for a fatal gang rape, saying it was unlikely to reverse the country's "rape crisis" despite a public clamour for their execution.

After a seven-month fast-track trial, Judge Yogesh Khanna said Friday the four men should be "hanged by the neck til they are dead" for the brutal rape of a 23-year-old woman on a bus last December.

Soon after the sentencing, people distributed sweets in the streets in celebration and tweeted that "justice" had been served.

But on Saturday, rights network Avaaz slammed the sentencing, urging the government instead to launch a mass public education campaign to stop India's "rape epidemic".

"Executing these men won't bring back the woman they raped or reverse India's rape crisis. The only way to stop rape before it starts is with a massive public education campaign," the online activist network said.

Indian newspapers splashed the sentencing on their front pages along with mug shots of the four convicts whose crime shocked the nation and triggered weeks of street protests.

"Showed no mercy, got no mercy" screamed a banner headline in the English language Hindustan Times while the Times of India said: "Death for four for dastardly, diabolical, brutal crime".

In the lead-up to the sentencing, there had been a huge outcry for the four -- Vinay Sharma, Akshay Thakur, Pawan Gupta, and Mukesh Singh -- to be executed for their attack on the physiotherapy student and her male companion on December 16.

The newspapers, however, wondered if handing down the death penalty in rape cases would make women any safer across the country.

Last year, there were 24,923 cases of rape reported in India, according to the government's official statistics. But the actual figure is believed to be far higher with experts saying women are reluctant to file complaints for fear of social stigma in the socially conservative nation.

An editorial in The Hindu newspaper was scathing in its criticism of the judgement, saying it would serve little purpose other than providing a "false comfort of retribution".

"In meting out the hangman's justice... the sessions court has regrettably missed an opportunity to turn the discourse away from retributive punishment to constructive dialogue on policing and legal reforms," it wrote under the headline, "Crimes death can't wish away".

The victim, who cannot be named for legal reasons, died of massive internal injuries on December 29 after being lured on to the private bus by the gang following a cinema trip with a companion.

The fifth suspect in the case, bus driver Ram Singh, died in prison in March in an apparent suicide.

A sixth member of the gang, who was a minor at the time of the assault, was sentenced last month to three years in a reformatory, the maximum penalty allowed under India's juvenile laws.

In handing out the sentence Friday, judge Khanna said the crime fell into the "rarest of rare category" that justified capital punishment under India's legal system.

Kavita Krishnan of the All India Progressive Women's Association said the punishment was hardly going to serve as a deterrent.

"In the same court, there were acquittals in 20 out of 23 rape cases. Potential rapists can see how remote their chances of conviction are, leave alone the punishment," she told AFP.

The Hindustan Times said the death penalty was "not an occasion to rejoice" because it would not stop sex crimes.

To make India safer for women, "we must tackle deep-rooted social problems", it said.

The Mint newspaper said hysterical celebrations by people outside the court were worrying.

"The mob seemed to go through some form of extreme catharsis. It was a terrible thing to watch, so many men and women in utter ecstasy because four men were set to die," it said.

Human Rights Watch called the punishment "troubling".

"It may have a popular appeal and seem like the easy option, but the government should abolish this inhumane measure and get down to the harder task of institutional reform," the group's regional director Meenakashi Ganguly said.

"That would be the way to really protect women and girls from future attacks," she added.