A technical hitch has affected Visa transactions across Europe, leading to some cards being declined without reason.
The problem first came to the attention of the UK-based firm at around mid-morning after customers in the UK and mainland Europe reported having transactions declined.
A spokesman for Visa Europe said the problem was short-lived and that a back-up system was in place by around midday.
Simon Kleine, head of external communication for the payments firm, added that minimal impact was caused and that most people would not have noticed a problem.
Visa were unable to put a figure to the number of people affected, but judging by the calls received, it estimated that hundreds of people had seen their card refused.
In a statement, Visa Europe said: "This morning, we experienced some technical problems in our card transaction processing, resulting in some card transactions being declined."