Three arrests have been made in connection with robberies in Amersham and Chesham Bois.
A 31-year-old man from Croydon, a 26-year-old man from Amersham and a 15-year-old boy of no fixed abode were all arrested on suspicion of two counts of robbery.
They remain in police custody.
The arrests relate to incidents in Ivy Stores, Plantation Road, Amersham on Wednesday 21 February and at the Londis Store, Bois Lane, Chesham Bois on Thursday 22 February. Both incidents happened around 5.30pm.
Detective Inspector Mark Hill, of South Buckinghamshire Priority Crime Team said: “We are very much in the early stages of the investigation and would urge anyone who may have been in these areas and who may have seen anything suspicious at these times to please contact police.
“You can contact us by calling 101 or making a report online quoting reference 43240083559.
“Alternatively, you can make a report online, or call Crimestoppers anonymously on 0800 555 111.”