Thousands of bank customers who were charged twice for transactions on their bank cards this week are to be refunded over the next few days.

The problem arose at AIB Merchant Services point-of-sale terminals on Monday this week and in some cases accounts were debited twice for transactions.

The merchants using the terminals were also credited twice for these transactions.

There were 88,000 transactions involved and it is understood it affected card holders from several banks.

In a statement this evening, AIB said that the transactions are processed by a company called First Data Inc.

It said the error was as a result of a technical issue in First Data's processing facility in Germany.

AIB said the sums involved will be processed tomorrow and refunds will appear on the customers accounts in the following days.