Police are investigating a serious sexual assault on a woman aged in her 20s in Omagh.
The attack was reported in the Fairmont Cottages area of the Co Tyrone town in the early hours of Sunday morning.
Detectives said: "We received a report at 3.05am that as a woman, aged in her 20s, was walking in the vicinity of Fairmont Cottages in the town, an unknown male grabbed her and dragged her into an alleyway beside Eastview Terrace where he sexually assaulted her.
"The attacker ran off when he was disturbed by a man who was walking past.”
The spokesperson went on: "This was a horrific experience for the victim, who has understandably been left deeply traumatised.
"I want to appeal to the man who disturbed the suspect to contact us to help us with our enquiries.
“I would also appeal to anyone who was in the area and saw what happened, or who has information which may help our investigation, to contact detectives on 101.”