The bank cards were cloned at points of sale in shops and restaurants around Dublin in the last few weeks.

It is understood that criminals paid shop and restaurant workers up to ten thousand euro to skim laser cards and find out their pin numbers by looking over their shoulder - a practice called "shoulder surfing".

The criminals withdrew cash from the unsuspecting victims in countries around mainland Europe, including Italy, Romania and Spain.

The largest single amount stolen from one account was 7,800 euro.

Most of the withdrawals took place at the end of April and in early May, and many of the customers contacted their bank themselves to notify them of the irregularities because the banks fraud detection systems failed to pick up on the activity.

"These people were obviously working for a number of days before they were detected," said a spokeswoman for the Irish Payment Services Organisation (IPSO).

"A member of a criminal gang would hire someone working in a shop or restaurant. They would be offered maybe up to 10,000 euro to get card numbers. And if they have any type of criminal instincts they take the money. "

"The people behind this are quite focussed. They come in, hire people on the ground, or carry out the skimming themselves."