A city centre lane was sealed off early yesterday following reports that a woman had been assaulted.
Police probing the alleged attack cordoned off Carmelite Lane and a force spokeswoman confirmed that a man had been arrested in connection with the incident.
She added: “A man has been detained and he is assisting police with their inquiries.”
She also appealed for witnesses to come forward, saying: “Investigations are at a very early stage but we would encourage anyone with information to contact police on 101.”
The lane, which runs between the Aberdeen Market, on Hadden Street, and Trinity Street, is understood to have been closed off just before 5.30am..
A local hotel worker said: “The lane was already closed off when I came into work at 7am and there were police officers standing on guard.
“My colleague, who was on the night shift, said police taped off the area at about 5.20am.”
Another worker, from a nearby pub, said: “I was here cleaning up the bar until about 4am and when I left I saw two uniformed police officers in the lane.
“You could tell they were looking for something.
“When I came back at around 10.45am, I saw the area had been sealed off.
Erin Law, a waitress and Cafe 52, on the Green, said she was “shocked” to hear of an alleged assault in the area.
She added: “I have not really heard of anything like that happening here in Aberdeen so it is surprising to hear.”
Martin Greig, chairman of Aberdeen Community Safety Partnership, added: “It is really shocking to hear of this alleged attack.
“Aberdeen was the first city in Scotland to win the purple flag award in recognition of significant improvements made over the years to make the environment of the city centre a safer place for everyone.”
“But there is never a time to be complacent when it comes to crime and antisocial behaviour and more efforts should be made to improve the lighting in this area and to ensure that potential victims are protected as far as possible.
“There is a great deal of collaborative work between police, the council, fire service and local businesses who are all working together to make our city centre a better and safer place.”