A "smartly dressed" attacker raped one woman and attempted to rape another in the space of 15 minutes in a city centre street.
The pair were walking home separately after a night out when they were sexually assaulted in Glasgow in an early morning attack on Wednesday.
Police said the first victim, a 20-year-old woman, ran from James Watt Street onto the Broomielaw and flagged down a taxi after she had been raped in a carpark nearby at around 3.55am.
As police arrived at that incident, the second victim, a woman aged 22, flagged down a passing driver further up James Watt Street after the same attacker attempted to rape her on an off-ramp at around 4.10am.
The sex attacker, who was wearing a shirt, tie and a "distinctive white or silver watch" had approached both woman separately on the street, before forcing them off the thoroughfare as they headed towards the Clyde end of it.
Detective Inspector Kate Jamieson, who is in charge of the investigation, said: "The man was very smartly dressed and may have been coming from a Christmas party or a night out with friends, family or work colleagues before the incident.
"He was wearing a fitted dark shirt or jacket, grey work trousers, a light tie and shoes as well as a quite distinctive white or silver watch.
"The man was seen wandering in the area for a significant period of time, which may jog anyone's memory. He forced the girls into areas off the main street after he had made a passing comment to both girls, which they didn't pay much attention too."
The first victim received hospital treatment after the attack and both were described as police as being "extremely distressed".
Strathclyde Police confirmed examination of CCTV in the area had caught the rapist on camera in the area as early as 3.30am. He was seen to be wandering around Cadogan, James Watt and Argyle streets as well as the Broomielaw before the attack.
Both of the victims tried to fight off the sex attacker after he approached them.
DI Jamieson added: "We are currently examining CCTV and carrying out extensive inquiries to identify the man responsible for these despicable attacks on two young women.
"I would appeal to anyone who was in or around the James Watt Street area of Glasgow around 4am this morning and who may have seen a man hanging around or noticed anything out of the ordinary to contact officers as soon as possible. I would also ask anyone who can help identify this man to contact us as a matter of urgency."
The victims are being supported by specially trained sexual offences liaison officers after the assaults.
Strathclyde Police cordoned off the street for several hours after the incident, while they have also released a description of the rapist in an attempt to track him down.
Chief Superintendent Val Thomson said that she was confident the attacker would be caught quickly.
She added: "Glasgow if a safe city to live, work and visit. The vast majority of the thousands visiting the city centre each night return home safely.
"Our advice is, if you are on a night out, try not to wander off alone and stick to the well-lit streets.
"In the coming days we will have additional police officers in the James Watt Street area and the Broomielaw."
The man is described as being in his mid-20s, around 5ft 8in to 5ft 10in, with a slim to medium build and light brown hair. A CCTV image of him was released by police on Wednesday evening.
Police said at the time of the assaults he was "smartly dressed" and was wearing a fitted dark long-sleeved shirt or jacket, light or possibly grey dress trousers, a light tie, a distinctive white or grey watch and shoes.
Anyone with any details regarding the attack should contact the city centre police office incident room on 0141 532 3159.