People are being warned to look out for anything unusual

Cards are then "cloned" so that cash can be withdrawn.

Trevor Bracken, from Cambridgeshire Police, said: "There has been increased activity in East Anglia recently, with offences being reported at Boston, Great Yarmouth and in Bedfordshire.

He cautioned people to use cashpoints covered by CCTV cameras.

He said criminals prefer to place cloning devices and tiny cameras on machines where no surveillance cameras operate.

He added: "These devices, when placed over the card slot, blend in with the machine and are almost impossible to detect.

'Out of order' ploy

"There will be a mini camera located to read the pin number as it is being typed; this camera can be concealed in a pamphlet holder or receipt bin attached to the machine."

"The advice I would give is, be particularly wary if adjoining cash points have 'out of order' stickers on them, as offenders have been known to use this ploy to divert customers to the machine they have tampered with.

"Additionally, when typing your pin number, shield the keyboard to prevent any camera recording your details."

Bedfordshire Police last week arrested two men for conspiracy to steal at the Sainsbury's supermarket cashpoint at Bells Brook in Biggleswade.

And on Saturday afternoon, police discovered a device attached to a cash machine at the HSBC bank on Market Hill in Cambridge.

Two men described as eastern Europeans grabbed the device and ran off.

A few hours later, a similar device was seen being placed on a cashpoint at the Tesco store in Wisbech. This machine was seized with no trace of the offenders.

A similar incident took place in Wisbech on 19 January.