The woman had been at a restaurant in the city when she was attacked by a 25-year-old man. No suspects had been detained by late Saturday evening.
Police see no immediate connection with an ongoing investigation into an extended string of rape attacks in the city.
“This crime is an isolated incident and the description of the suspect does not match with other similar incidents,” Peter Persson at Örebro police said.
Örebro police have been working with a series of unsolved rapes and sexual attacks that have occurred in the city over the past five years.
In a separate case a 23-year-old man was arrested last Monday after three new attacks were reported over the weekend, originally believed to be perpetrated by the same person.
The man was arrested at around 7pm last Monday evening on suspicion of rape and attempted rape after a broad police manhunt following the attacks on a 23-year-old and 64-year-old woman.
The man was later remanded into custody and has since confessed to a rape committed in March.