A thief used a gun to threaten a shop assistant and steal money from a Marks and Spencer.
The armed robbery happened at a food hall on Lochavullin Drive in Oban at 3.20pm on Tuesday.
A 17-year-old shop assistant was threatened before the thief stole a three-figure sum of cash.
The attacker is 6ft, between 45 and 50 years old, slim and was wearing a green khaki jacket, outdoor boots and a black beanie hat.
Inspector Scott Hamilton described the robbery as “very frightening”.
He said: “This was a very frightening experience for the young shop assistant and anyone else who was within the shop at the time and thankfully no-one was physically hurt.
“We are currently making enquiries in the area to establish where the culprit went to when he walked out of the shop.
“Anyone who recognises the description of the suspect or thinks they may have seen him hanging around the area either before or after the robbery took place is asked to contact police at Clydebank immediately via 101.”