Visa says its service is “close to normal” following a system failure which left customers across Europe unable to pay for some purchases.
The company apologised and said it had no reason to believe the hardware failure was down to “any unauthorised access or malicious event”.
Shoppers had reported being stuck in queues as Visa transactions could not be processed.
Mastercard and American Express were not affected by the problem.
Payment processing through Visa’s systems accounts for £1 in £3 of all UK spending, the company said.