Detectives are currently questioning three Sheffield men in connection with two armed robberies at convenience stores earlier this week.
The men, aged 29, 32 and 34-years old, were arrested on Wednesday on suspicion of robbery and remain in police custody today.
Two men entered a Spar store on Stannington Road at around 9.30pm on Sunday, 27 September.
Staff at the store were alleged to have been threatened with a knife.
The pair left the store with cash and a quantity of cigarettes.
On Tuesday, September 29, three men entered a One Stop Shop on Cottam Road in High Green at around 9.55pm.
The two incidents are thought to be linked.
Staff were allegedly threatened with a knife before the men left with a substantial amount of cash.
The alleged incident in High Green is the fourth armed robbery in as many days across the city.
In a separate incident, two men wearing Halloween masks threatened terrified shop staff with a gun and made off with £500 at a Co-op store in Norton Lees last Sunday around 7.20pm
Another incident in Grimesthorpe left a man hospitalised after suspects left the store with £50 at 6.45pm on Sunday.
The incidents are not thought to be linked.
If anyone has information or believes they may have witnessed the incidents, contact police on 101, or Crimestoppers anonymously on 0800 555111, quoting incident number 1172 of 29 September.