NEW DELHI: An Indian court found a teenager guilty on Saturday of taking part in the fatal gang-rape of a student in New Delhi last December.

The juveniles' court sentenced the teenager to three years in a correctional facility after handing down the first and long-delayed verdict over the brutal assault on a student on a moving bus in 2012.

“He has been held guilty for rape and murder and sentenced to three years subject to review,” Anil Sharma, the chief investigating officer in the case, told reporters outside the court.

The verdict was delayed after a petition was lodged in the Supreme Court by an opposition politician Subramanian Swamy, who argued that those over 16 should be tried in adult courts if involved in very serious offences.

The teenager, who was 17 at the time of the attack, was given the maximum penalty after he was tried as a juvenile. The sentence includes the time he has already spent in custody.

The victim's mother emerged from the court in tears, disbelieving of the sentence.

“He should get an adult sentence,” said the emotional mother.

Her daughter, a 23-year-old physiotherapy student, died of internal injuries after being raped and assaulted with an iron bar allegedly by six men on the night of December 16, 2012.

Her male companion was also beaten up before both were thrown from the bus.

The attack sparked weeks of sometimes violent protests all over the country.

The victim's family had earlier called for the teenager to be given the death penalty, saying the juvenile justice system was too lenient, as it sought to reform rather than punish perpetrators.

Outside the court, up to 20 protesters demanded a harsher punishment, screaming “Hang the juvenile too” and “We want justice.”

A separate trial of the four adult suspects is hearing closing arguments and is expected to come to a decision in the next few weeks. The men face a possible death sentence if convicted.

The fifth adult, the suspected ring leader, died in jail in an apparent suicide soon after his arrest.

National outrage over the attack pushed parliament to pass a new law toughening sentences for rapists.

The Supreme Court this month cleared the way for the principal magistrate, Geetanjli Goel, to deliver the verdict on the juvenile's case.

The juvenile, one of six children, was employed to clean the bus allegedly used for the attack and often slept rough or inside the vehicle, reports say.

He reportedly left his impoverished home in a village in northern Uttar Pradesh state at the age of 11 to live in Delhi, where he worked in a string of menial jobs until landing the job of bus cleaner.

Children's rights groups in response to the sentence, have called for public restraint over the verdict, saying the teenager needed to be given a chance of rehabilitation, adding that India's child protection services had already failed him.