Doctors say that the next 48 hours are critical for her; they described the injuries to her intestines and private parts as "extremely serious."
The student was on her way home after watching The Life of Pi at a South Delhi mall with a male friend. When the couple boarded a bus at about 9 pm, a group of men who were on the bus began harassing her, asking why she was out late with a man. When her friend tried to intervene, he was gagged and then hit mercilessly with an iron rod. Six men then hit the woman with the same rod and gang-raped her while the driver kept the bus moving. At about 11 pm, the couple was thrown semi-naked onto the road. (Read: How police cracked Delhi gang-rape case)
A passer-by phoned the police which then collected the couple and moved the pair to hospital.
The private bus was used by two schools but the driver was moonlighting on Sunday night, hoping to make an extra buck.
Delhi's Health and Welfare Minister Kiran Walia said the victim had been "tortured." "Doctors say she is very critical. The abdomen and the intestine are not in the right place. This is an absolutely abominable act and I condemn it," she said. (Read: Angry MPs ask govt for tough action, more security)
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