During one incident offenders tried to use a fire extinguisher at residents.
Police are appealing for witnesses after three Post Offices were burgled across West Oxfordshire and South & Vale.
The incidents all took place within an hour of each other on Thursday.
Offenders forced entry to the one on Broad Street, Uffington, by smashing the glass at around 3.15am. Once inside, they stole cigarettes, tobacco and an amount of cash and left the scene in a vehicle.
Five minutes later a group of four men were disturbed by a member of the public on Marlborough Close, Faringdon, as they were hanging around a resident’s parked car. The men left the scene in a grey Audi A6 estate car with a loud engine.
Shortly after that offenders forced open the front door to the Post Office on Market Square, Bampton which activated the alarm. They tried to use a fire extinguisher at the witnesses before leaving the scene in a vehicle. Cigarettes and cash were stolen.
Finally, at around 4.10am offenders forced entry to the Post Office on St Michaels Close, Shipton Under Wychwood, Chipping Norton and stole cigarettes and cash.
The offenders were all wearing dark clothing with their faces covered.
Investigating officer Detective Sergeant Timothy Hawley based at Banbury police station, said: "I believe that these incidents are linked.
"If anyone has any CCTV footage from the time of the offences or thinks they saw anything suspicious around the time, please contact the 24-hour non-emergency number 101, quoting 43190235460 or make a report online.
"“If you don’t wish to speak directly with police, you can call the independent charity Crimestoppers 100% anonymously on 0800 555 111."