The incident took place in the city of Halle in Saxony-Anhalt on Friday night. The victim's 34-year-old ex-partner has been arrested on suspicion of carrying out the attack.
Police say the victim was accosted outside her front door and that the attacker took her to the building's cellar, where he poured liquid over her and set her ablaze. The woman managed to escape and run onto the street, her body still burning. Passers-by helped put out the fire. One woman sustained injuries of her own.
The suspect fled but was pursued by a pedestrian and subsequently arrested by the police. He's been charged with attempted murder and aggravated assault. His motive is unknown.