A further three defendants were given life sentences for the gang-rape of the victim.
The court handed down the sentences following their conviction on Thursday. The 21-year-old woman was targeted as she walked home after an exam in 2013 in Kamduni village in West Bengal.
Senior public prosecutor Anindya Raut said: “It was a gruesome crime, a rarest of the rarest case.”
Additional District and Sessions Judge Sanchita Sarkar handed down the verdicts in a packed court which included the victim’s family.
“I award the death sentence to three convicts on charges of gang-rape and murder of the student and life imprisonment to three others for gang-rape, criminal conspiracy and causing disappearance of evidence,” Sarkar said.
Those sentenced to death were Saiful Ali, Ansar Ali and Amin Ali.
Sheikh Emanul Islam, Aminur Islam and Bhola Naskar were sentenced to life imprisonment.
Scores of activists and people from the victim’s home village were at court chanting slogans against the convicts and demanding death for all of them.
Extra police officers were deployed outside the court following a scuffle on Thursday between police and protesters who tried to enter the court complex.
“Justice has failed us as two of the accused were acquitted and three were awarded life sentences,” the victim’s brother said.
The woman, who cannot be named for legal reasons, was grabbed after getting off the bus before being dragged to a nearby abandoned farm.
The gang attacked her as she returned from the university to her home in the village, 50km northeast of Kolkata, on June 7, 2013.
She was found gagged and lying in a pool of blood in a field the next morning. Evidence showed she had been repeatedly raped.
Two of the eight accused were acquitted for lack of evidence by the court.
Defence lawyer Phiroze Edulji said the convicted men would challenge the verdict in the high court.
Raut said the victim’s family would also challenge the verdict as all eight accused should have been convicted.
During the hearing ahead of sentencing, Edulji said the case did not fall under the rarest of rare and as such did not warrant the death penalty.
He cited several Supreme Court judgments arguing that convicts have not been awarded death penalty even in cases that were more heinous than the current case.
Opposition leader and Communist Party of India (Marxist) state secretary Surjya Kanta Mishra said justice was done.
“Delayed, incomplete but justice nevertheless... Battle must continue in Kamduni and everywhere,” Mishra said on Twitter.
The residents of Kamduni, led by Tumpa Koyal and Moushumi Koyal who had formed a forum seeking death penalty for all the accused, hailed the verdict saying their fight for justice has been vindicated.
The attack triggered anger in West Bengal and came just months after the fatal gang-rape of a student in Delhi in December 2012 that shone a global spotlight on violence against women in India.
The 2012 incident led to an overhaul of India’s rape laws including speeding up of trials and tougher penalties for offenders, but high numbers of assaults persist.