A woman who survived an alleged gang rape and four separate acid attacks has once again been hit by corrosive liquid, Indian police said Sunday.

The 35-year-old mother, who was allegedly gang-raped in 2008 over a property dispute, was at a women's hostel in Lucknow, the capital of Uttar Pradesh, when a man scaled the walls and poured the chemical on to her.

"She was filling water at the hand pump when the attack took place. The attacker fled from the spot," Vivek Tripathi, local police chief told AFP.

The woman, who cannot be named for legal reasons, sustained burn injuries to her face and shoulder and is undergoing treatment at a hospital. Police have launched a manhunt to identify the assailant, the officer said.

Due to the previous string of attacks, the woman was under around-the-clock police protection, but the armed policeman was barred from entering the women's hostel.

The woman was allegedly gang-raped and attacked with acid by two men in 2008 over a property dispute. She has subsequently been attacked twice more by the same men, in 2012 and 2013, in a bid to force her to withdraw the criminal cases against them.

Most recently, the two men allegedly forced her to drink acid while she was travelling on a train with one of her daughters in March this year. The men are facing trials over all the attacks, but they were released on bail in April.