And then, the police said, the men beat the couple with an iron rod and repeatedly raped the woman as the bus circled the city. The woman suffered severe injuries to her head and intestines and required multiple operations, local news media reported, indicators of an assault so savage that New Delhi on Tuesday was shaking with public outrage. Protesters encircled a police station and blocked a major highway. India's Parliament erupted in angry protests and condemnation.
"A terrible, terrible atrocity has happened," Renuka Chowdhury, a Member of Parliament, said Tuesday during a raucous session in the upper house. "I am not going to allow this incident to become another statistic."
Sushma Swaraj, the leader of the opposition in the lower house, demanded that the death penalty be imposed for rapists. "She will live her whole life as a living corpse if she survives," Swaraj said of the victim. "Why should there not be the death penalty in such a case?"
Horrific cases of violence against women seem to happen with disturbing regularity in northern India, many of them occurring in the national capital, now often described in the media as India's rape capital. In one highly publicized case in September, a 16-year-old girl in the neighbouring state of Haryana was raped repeatedly by a group of eight men, perhaps more, who recorded the assault on their cellphones and threatened to kill her if she told anyone. But the family came forward after the videos circulated, and her father killed himself by drinking pesticide.
The New Delhi attack occurred on Sunday evening, in the southern rim of the capital. The woman, a 23-year-old medical student, had been out with a male friend; Indian news media reported that they had seen a film together. It was about 9:10, and the police said the couple were trying to find a ride to a city neighborhood known as Palam. A bus pulled over, and they boarded.
New Delhi has a mix of public and private buses serving more than 7 million people every day. The police said the man and woman had been tricked into believing that the bus was part of the city's public fleet: one of the suspects was posing as a conductor, calling out for passengers. Instead, the bus was owned by a private charter company. One of the suspects worked for the company by day, driving a bus for a private school.
As the bus began moving, three young men confronted the couple and began harassing the woman, the police said. Her friend tried to intervene, but they beat him with an iron rod and then repeatedly raped the woman, the police said.
Eventually, the two were stripped of their clothing and thrown out of the bus onto a national highway on the southern outskirts of the capital.
In a briefing on Tuesday afternoon, the Delhi police commissioner, Neeraj Kumar, said the suspects had taken the bus after an evening of drinking and eating. "The idea was to have fun," he said.
The police said they had arrested four of the six suspects in the case, based on evidence from closed-circuit surveillance cameras. The commissioner said the courts would be asked to "fast track" the case, while prosecutors are expected to seek the maximum sentence of life in prison.
The woman is being treated at Safdarjung Hospital in New Delhi, and regained consciousness on Tuesday, local media reported. She is communicating through writing.
Across New Delhi on Tuesday, women's groups and students organized protests to demand better security, at one point shutting down the city's outer ring road, a major route. Several hundred other protesters gathered around the police station where the complaint had been filed, holding placards and chanting slogans.
"This is an expression of our horror and anger and discontent at how things are," said Komal, a doctoral student at Jawaharlal Nehru University who asked to be identified only by her first name. "The government has to take responsibility."
She said she regularly took buses and often felt unsafe traveling in the capital region. Being sexually harassed is an "everyday experience," she said. Women are constantly followed by men and groped while on public transportation, she said.
Anupama Ramakrishnan, 33, who is studying sociology at Delhi University, blamed what she called "a deeply held sense of patriarchy" for the attack.
"This is not about sexuality," she said. "It is about power and violence."
New Delhi has one of the highest reported rates of crime against women in India, though most experts believe that the official numbers barely hint at the real scale of the problem. Nearly 600 rapes were reported last year, according to the National Crime Records Bureau, more than the reports from Mumbai, Chennai and Bangalore combined. This year, the capital has recorded more than 600 rapes and may set a record.
In northern India, reports of rape are often followed by questions about the victim's behavior, and even accusations that she provoked the assault.
On Tuesday, some of India's most prominent activists and social commentators took to Twitter to voice their opinions.
"Security in mobility for a woman is the first right she needs to be guaranteed!" wrote Kiran Bedi, once one of India's highest-ranking female police officers. "Failure to ensure this is clear failure of governance!"
(Hari Kumar contributed reporting.)
© 2012, The New York Times News Service