Four men have been arrested with five crimes that Derbyshire Police believe are all connected.
The men are currently in custody and will be interviewed today. Two are aged 53 and 30 and from Ilkeston, one is 34 and from Derby and one is 30 and from Stapleford.
A police spokesman said: “In recent weeks, we have had reports of an aggravated burglary and a robbery in Sandiacre and robberies at shops in Spondon, Kirk Hallam and Ilkeston.
“We now believe the crimes are connected and are asking the public to assist us with our enquiries.”
The latest incident was a robbery at the One Stop in Charlotte Street, Ilkeston, at around 10.50pm on Monday, February 6. The men threatened staff with a knife and took cash.
At around 9.50pm on Friday, February 3, a robbery took place at the Co-op, in Ladywood Road, Kirk Hallam. They went around the back of the counter and took cigarettes and cash from the till before leaving.
The Co-op in Chapel Street, Spondon, was robbed at 2.40pm on Monday, January 30. The cashier was threatened with a knife and cash and tobacco was taken.
Men entered the Diamond Spa massage parlour in Derby Road, Sandiacre just before 7pm on Sunday, January 29. They went in posing as customers but produced a knife and took cash and mobile phones.
The first crime happened at 7.20pm on January 24 when men went into a house in Barker Avenue North, Sandiacre and threatened a man inside. They took phone, cash and jewellery.
Detective Inspector Richard Burton said: “We are asking the public who may have been in the area of the crimes at the relevant times to help us with any information they can offer.
“The offenders wore masks or balaclavas which would have appeared out of place. If you have any information, no matter how small in relation to these incidents, I would urge you to get in touch.
“We are visiting shops across Erewash and Derby to speak to staff about security and reassure customers.”
Witnesses or anyone with information should call DI Richard Burton on 101, quoting reference 17000034304.