The attack, which was reported to police at 3.30am, took place in a yard at the rear of The Vine pub on The Headrow. The scene is currently being examined as part of the investigation.
The victim had been in The Headrow when she was dragged down the alleyway next to the former Big Lil’s pub and subjected to a serious sexual assault.
Her attacker was described as black, 5ft 8ins tall, aged in his late twenties, with short hair. He was wearing a black hooded top.
The victim is being supported by specialist officers from the Force’s rape investigation unit.
Enquiries have shown there were a number of other people in the area around the time of the incident who may have seen the man involved. Detectives are appealing for anyone who was there to get in touch.
Anyone with any information should contact the Homicide and Major Enquiry Team via 0845 6060606 or call Crimestoppers, anonymously and in confidence, on 0800 555 111.