The attack happened at around 1am on Sunday when a 25-year-old was approached by another man as he walked on Brooms Road at its junction with Millburn Avenue.
Detectives say the victim was forced to a nearby grassy area where he was subjected to a serious sexual assault.
The attacker then fled along Brooms Road in the direction of Morrisons supermarket.
He is described as being around 6ft 1in, with a stocky build and a possible foreign accent. He was wearing dark clothing and a hooded top.
Detective Inspector Scott Young said: “A young man has been subjected to a terrifying sexual attack and extensive inquiries are under way to find whoever is responsible for this utterly despicable crime.
“I would like to speak to anyone who was in the area near to where Brooms Road meets Millburn Avenue between midnight and 2am on Sunday morning.
“Whether you saw a man matching the description of the suspect, a man following another man, or a man in a state of distress - if you saw anything out of the ordinary at all then please come forward.”