The victim, stated officers, was attacked at the foot of Friars Vennel.
A spokesman said: “Three men were seen running up Friars Vennel in the direction of the Douglas Arms pub after the assault.”
They have issued descriptions of the men:
The first is said to have short dark hair, slim build wearing blue denim shirt with white sleeves and blue jeans.
The second had short brown hair, muscular build, wearing a khaki coloured t-shirt and black jeans.
Finally, the third had short dark hair, was of medium/large build, had dark coloured polo top and dark blue jeans.
A police spokesman added: “Police would like to hear from anyone who may have witnessed this incident or have knowledge of those involved.”