A bogus police officer forced a car to stop before attacking a man and stealing the keys.
Two people in a Mercedes were pulled over at Strathclyde Park, Hamilton, by a dark SUV using blue and red lights just after midnight on Monday.
A blonde-haired man dressed like a police officer and wearing glasses asked both of them to get out the car, before assaulting the male passenger and taking the keys. He then made off in the SUV.
Police are appealing for anyone with information to contact them.
Detective constable Gary Lipscombe said: “I’m aware that the circumstances of the crime will be of a concern to the public, but rest assured we are working hard to identify the suspects.
“We are currently studying CCTV footage from the surrounding areas and are gathering more detail on the car used by the suspects.
“I would also like to remind the public that police officers carry warrant cards that can be produced on request.
“I am appealing to members of the public who may have been in and around Strathclyde Park, Hamilton area around the time of the incident.
“In particular, to motorists with dash cams, it’s possible you could have captured images which could assist our investigation, so please check your footage.”
Anyone with information should call police on 101.