Police and bank managers in Athens, Thessaloniki and other cities across the country have intensified cooperation in a bid to crack down on the activities of criminal rings believed to be swindling thousands of euros from unsuspecting bank customers by copying their bank card details using devices planted at bank ATMs. Most of the rings are believed to be run by foreign nationals, chiefly from Balkan states, and it is thought that the bank details garnered by the devices are being used in illegal transactions carried out abroad as well as in Greece. Police in Thessaloniki yesterday detained two Bulgarians believed to have been using cloned bank cards to swindle thousands of euros from cash machines in the northern city. Officers confiscated 4,350 euros following a raid on the homes of the suspects, aged 27 and 44. Earlier this week, police in Thessaloniki arrested two Romanian nationals, aged 29 and 32, believed to be members of a major ring copying bank card details from ATMs and using the data to create clone cards which they then used to tap into several bank accounts. Similar devices have been planted in provincial towns too, with cases of cash-machine fraud reported earlier this month in Karditsa, central Greece. According to police, the devices planted at ATMs by ring members are «hardly discernible and extremely effective» and more sophisticated versions are appearing all the time. Police have traced nine such devices in ATMs across Attica since the beginning of the year and 30 last year. Often the devices are not visible, as they are inserted directly into the ATM’s cash card slot. One such device, confiscated from a foreign national arrested in the Athens district of Zografou earlier this week, was found to contain data from 17 different bank cards. During questioning, the suspect allegedly admitted to having acquired the details of an additional 29 cards using the same fraudulent techniques.