Thames Valley Police is appealing for witnesses after a robbery at the BP Garage, on the A40 in Gerrards Cross on Monday night.
At around 10.40pm three men wearing balaclavas or face coverings entered the BP Garage and threatened the staff on duty, assaulting one of them.
They then stole a large quantity of cigarettes from the shop and drove off in a silver BMW three-door coupe.
The victims sustained minor injuries, but did not require hospitalisation.
The three offenders were men all thought to be white. One was wearing a black hooded top with black track suit bottoms, black gloves and black shoes.
The second offender was wearing a white hooded top over a grey top, with black tracksuit bottoms and white trainers with blue markings. He was wearing a black balaclava and black gloves.
The third offender was wearing a white top with red face covering and black gloves.
Anyone with information is asked to contact detective sergeant Richard Earl of Force CID at Amersham via the Thames Valley Police Enquiry Centre on 101, or they can contact Crimestoppers anonymously on 0800 555 111 or online at www.crimestoppers-uk.org.