An Indian student was recovering in hospital after being gang-raped by a group of men including some charged with sexually assaulting her three years earlier, an officer said Monday.

Police in Haryana state were hunting for the five, accused of abducting the 21-year-old student of the lowest Dalit social caste from outside her college before drugging and raping her in a car.

The student was found unconscious in bushes on the side of a highway last Wednesday night in Haryana which borders New Delhi, in the country's latest shocking sexual attack.

Haryana deputy superintendent of police Pushpa Khatri said the student, who is still in hospital, has identified all five men -- two of whom are currently on bail awaiting trial for raping her in 2013.

"She has identified the five accused and two of them were involved in the gang-rape of the student in Bhiwandi district in 2013," Khatri told AFP.

"We have formed several teams to arrest the accused."

The woman's family has accused the five of threatening them in the lead-up to Wednesday's attack, demanding that they withdraw the rape case lodged after the 2013 assault.

"The accused were constantly threatening us to compromise outside the court. They even offered us a hefty amount for settlement. But we didn't agree," the victim's brother was quoted by the Hindustan Times as saying.

The family also alleged they were forced to move to Rohtak district in the state from a neighbouring district after the 2013 attack because of harassment by the accused.

Members of the Dalit caste held small protests in Rohtak on Sunday to demand justice for the victim.

The fatal gang-rape of a student on a bus in Delhi in 2012 shone a global spotlight on frightening levels of violence against women in India.

It also led to major reform of India's rape laws, including speeding up of trials and increased punishments for offenders, but horrific attacks continue to be reported in the media on a daily basis.

The most recent official figures show that 36,735 rapes were reported across the country in 2014, although activists say the true number is likely much higher because of the social stigma attached to sexual crimes.