The plastic device, known as a "Lebanese loop" is attached to the front of a cash machine and looks like part of the mechanism, but it causes inserted cards to remain inside.

The thief stands behind the victim making a note of their PIN and, once the person enters the bank to try to get the card back, the offender withdraws cash from their account.

West Mercia Police said banks in Newport and Shifnal had been targeted over the last few days and warned people to be on their guard.

A spokesman said after one incident, in Shifnal, five transactions were made, within the space of a few hours, in locations as far apart as Telford and London.

A total of �1,000 was withdrawn.