AIB has assured customers that an error which caused some debit transactions to be duplicated earlier this week has now been rectified.

The issue arose after a file of debit card transactions was processed twice in error.

The mistake caused an undisclosed number of customers to be charged twice for the same transactions on March 25th and then again on March 26th.

The issue affected customers who used their cards at merchant terminals in retail outlets.

The bank said this afternoon it had completed reversing the impact on customer accounts, and apologised to customers for the disruption.

“AIB regrets any disruption to our customers arising from duplicate transactions processed on their accounts,” it said in a statement.

“We apologise for any inconvenience caused and will ensure no customers will be adversely affected.”

It is unclear if the error left some customers without access to funds for a time.

A spokeswoman said none of the affected customers would be left out of pocket as a result of the duplication error.

She later clarified that this included any referral fees incurred as a result of the issue.

In January, Bank of Ireland customers were mistakenly debited twice for single transactions involving mainly Visa debit cards - the bank's main debit card product.

The problem arose from the duplication of a file and not from a technical glitch in the bank’s processing system.