The attack took place in the Gurdaspur district of Punjab province
The victim had boarded the service to visit her in-laws when she was abducted and driven on a motorbike to a house in Gurdaspur district, bordering the city of Amritsar, in Punjab province, on Friday evening.
Five men, including the driver and conductor, took it in turns to rape the woman before dropping her off near the village where her in-laws lived the following morning.
The alleged attack comes just weeks after the gang rape and murder of a 23-year-old medical student on a bus in Delhi which has sparked nationwide protests about violence against women.
"Six men have been arrested on allegations of having raped a 29-year-old woman ... after forcibly taking her to an unknown location on the night of January 11," local police officer Raj Jeet Singh said, adding that a seventh suspect was being hunted.
"The lady, after being kidnapped, was raped brutally throughout the night by the seventh accused," he continued.
"After raping the victim throughout the night, one of the accused dropped her near her in-laws' house the next morning where she narrated the whole incident to her sister-in-laws."
The extent of the victim's injuries are yet to be established, the police officer added.
