A 23-year-old rape victim, who was set ablaze on Thursday by a gang of men including the alleged rapist as she made her way to court in northern India, is in critical condition and there are "minimal chances of [her] survival", Hindustan Times reported on Friday.

"The victim is in very serious condition. There are minimal chances of survival. Now, we have put her on [a] ventilator," the report quoted the medical superintendent of Delhi's Safdarjung Hospital Dr Sunil Gupta as saying.

According to Hindustan Times, the victim, who suffered 90 per cent burns in the attack, was airlifted from Delhi to Lucknow yesterday.

All five men have been detained, Uttar Pradesh police said in a tweet.

The woman attacked and burned on Thursday morning had been on her way to catch a train in Unnao district to attend a hearing when she was doused with kerosene and set on fire, police said.

"As per the victim's statement, five people were involved in setting her on fire, including the one who was accused in the rape case," a police superintendent in Unnao Vikrant Vir told Reuters.

Police documents seen by Reuters showed the woman had filed a complaint with Unnao police in March alleging that she had been raped at gun point on December 12, 2018.

Having been subsequently jailed, the alleged rapist was released last week after securing bail, police officer S.K. Bhagat said in Lucknow.

Uttar Pradesh is India's most populous state and has become notorious for its poor record regarding crimes against women, with more than 4,200 cases of rape reported there in 2017 – the highest in the country.

The Uttar Pradesh state government, currently controlled by Prime Minister Narendra Modi's Bharatiya Janata Party, came under fire in July from opposition groups accusing it of protecting a lawmaker accused of rape.

During the past week, thousands of Indians have protested in several cities following the alleged rape and murder of a 27-year-old veterinarian near the southern city of Hyderabad.

On Friday, Indian police shot dead the four men suspected of raping and killing the veterinarian.