Germany's Commerzbank said Wednesday it had decided to replace the bank cards of some 35,000 clients over fears account data may have leaked.
"To protect our clients from possible abuse we are exchanging their credit cards as a preventative measure," Commerzbank, Germany's second-largest lender, said in a tweet.
A bank spokesman confirmed a report in the German business daily Handelsblatt that a supplier may have left client data accessible to third parties.
The newspaper reported the company was a supplier of Visa and Mastercard.
Commerzbank said other banks also had client data potentially exposed.
Postbank, a subsidiary of market leader Deutsche Bank, will replace 55,000 cards according to Handelsblatt.