Visa was hit by a technical glitch across Europe last Friday (13 April), which prevented card payments from being processed.
Danish payments body Payment Business Services (PBS) was one of the first financial bodies to report problems, saying all Visa transactions were being rejected from midday.
Visa said that not all transactions across Europe were rejected, and that some countries were affected more than others.
While France and Italy are said to have avoided the processing glitch, a number of transactions are believed to have been affected in the UK.
Visa said the most seriously affected countries were in Scandinavia and central Europe.
The credit firm said it expected services to soon resume to normal, with many affected transactions able to be completed using a data back-up system.
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