A gang of young thugs carried out three robberies in three days on the same street.
The group targeted their victims in Hutchinson Walk, St Peter's, Leicester, on Thursday, Friday and Saturday.
Detectives believe the victims, aged 28, 34 and 38, were targeted for their mobile phones.
Two were threatened and hit before the thugs searched their pockets and grabbed their handsets.
However, one of the victims managed to run away before his phone could be taken.
The gang members are black and thought to be aged between 16 and 20.
Police have stepped up patrols in the area in response to the attacks.
Inspector Bill Knopp, commander of Spinney Hill Park police station, urged people to call police about any suspicious behaviour.
"It works really well when people call us as soon as they see something which is not right," he said.
"We had a call from a member of the public in Highfields today that they had seen some people in an alleyway putting on balaclavas. As a result of that call, we arrested two people.
"The inquiry is still at the early stages, but we believe that call has possibly prevented a serious offence.
"At the moment, we are not linking those arrests to the robberies in Hutchinson Walk.
"The wider picture is that robberies have fallen by 25 per cent in this area.
"These offences do tend to come in peaks and troughs and Hutchinson Walk has featured before."
A resident of Lincoln Street, which is near Hutchinson Walk, said: "It's scary that there could be three people robbed in a couple of days.
"I hope the people who were attacked are okay and that the police catch the animals who did this. If they can attack three people like this, they will do it again."
Detective Constable Jonathon Davies, who is investigating the robberies, said: "The victims were very upset and shocked and reported the incidents in the hope those responsible will be brought to justice.
"We are doing all we can to locate the offenders and have increased patrols in the area, but we hope that members of the public will also be able to help us.
"If you witnessed any of these incidents, we would urge you to get in touch.
"We know that there was a man in the area at the time of the incident on Friday who spoke to the group.
"If that man is you, please get in touch."
Contact Det Con Davies by calling 101. Alternatively, ring Crimestoppers, which is anonymous, on 0800 555 111.
