At 1.38am today, police received a report of a man being raped near to the Boulevard Public House, on the city's Churchill Street
They are appealing for witnesses.
An investigation is underway and a section of the area has been cordoned off while inquiries are carried out.
Today, there are extra officers in the area carrying out patrols and speaking to people.
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A 29-year-old man has been arrested in connection with the incident and is currently in custody.
Anyone who was in the area at the time of the incident, and who saw or heard anything, is asked to contact police on 101 quoting reference number 45 06/12/16.