A judge sentenced four men to death Friday for the fatal gang rape of an Indian student on a bus last December, triggering applause inside the packed courtroom.

Judge Yogesh Khanna told a court in the Indian capital that the case, which sparked widespread anger against the treatment of women in the country, fell into the "rarest of rare category", which justified capital punishment.

"In these times when crimes against women are on the rise, court cannot turn a blind eye to this gruesome act," he said.

As the courtroom burst into applause, the father of the 23-year-old victim told reporters that he was delighted with the sentence.

"We are very happy," said the father, who cannot be named to protect the identity of his late daughter.

"Justice has been delivered," he told reporters inside the court, flanked by his wife and sons.

His wife said that her daughter's "wish has been fulfilled at last".

One of the men, Vinay Sharma, broke down in tears as the sentence was announced, according to an AFP correspondent.

All four suspects were teary eyed as they entered the cramped room to hear their punishment after they were convicted on Tuesday of a string of charges including murder and gang rape.

There had been a huge clamour for the four -- 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.

After prosecution lawyers argued on Wednesday the gang were guilty of a "diabolical" crime, the victim's mother had implored the judge to hand down the death sentence.

Police in riot gear maintained a heavy presence outside the court on Friday with the road leading up to the complex barricaded off.

India had an unofficial eight-year moratorium on capital punishment until last November, when the only surviving gunman from the 2008 Mumbai attacks was executed. Weeks later, a Kashmiri was hanged over his role in an attack on parliament a decade ago.

During Wednesday's hearing, defence lawyers argued Judge Khanna should resist "political pressure" and instead jail the gang for life, citing the youth of their clients, who are all in their teens or 20s.

The gang's relatives had also been pleading for their lives to be spared ahead of the announcement.

Handing down his verdict at the end of a seven-month trial Tuesday, Khanna found the men guilty of the "cold-blooded" murder of a "helpless victim" whose fight for life won her the nickname of Braveheart.

Feelings have been running high in a country disgusted by daily reports of gang rapes and sex assaults on children.

A total of 1,098 cases of rape have been reported to police in Delhi alone so far this year, according to figures in The Times of India on Friday.

That represents a massive increase on the 450 recorded in the same period last year, although campaigners say the rise reflects a greater willingness by victims to come forward after the December bus attack.

Since the convictions, newspapers have printed graphic details of the onslaught against the student, including of the internal injuries she suffered while being violated with a rusty iron bar before being thrown naked off the bus.

Her injuries were so severe that she died nearly a fortnight later in a Singapore hospital. Before her death she had briefly regained consciousness, telling family and friends of her desire to see her attackers burn to death.

Lawyers for the men have already said they will appeal the convictions in the Delhi High Court, which will spell years of argument and delays in India's notoriously slow legal system.

In appeal, the defence is likely to advocate lesser sentences for some of the gang, and argue it was a "spur of the moment" crime and not premeditated.

There was widespread anger after a juvenile who was convicted last month for his role in the attack was sentenced to just three years in a correctional facility -- the maximum allowed by law.

The gang all lived in and around Ram Dass Camp, an unauthorised slum in southern Delhi where former neighbours had called for their execution.

"They deserve the harshest punishment... Reform is out of the question," said Maur Singh, a one-time neighbour who promised to hand out sweets in celebration if the judge sent them to the gallows.

Rattled by the mass protests, the government rushed through new anti-rape laws and ordered the trial be held in a special fast-track court.