Citibank Japan, the Japanese consumer banking unit of Citigroup, has admitted that flaws in its internal computer systems resulted in up to 275,000 incorrect transactions over the past few days.
Although Citibank has now fixed the problem, it is expected that thousands of its Japanese customers will be affected, with some transactions double booked, while others failed to be recorded at all after being processed.
In a statement, Citibank Japan said that it "deeply regrets that this incident has occurred".
"The bank is taking the necessary measures to prevent further occurrence," it added.
The latest mishap by Citibank, part of one of the world's biggest financial institutions, will not help its already tarnished image in Japan, where financial regulators have already has already expressed their dissatisfaction with the bank.
Only last month, Japanese regulators accused Citigroup's Japanese trust banking unit of misleading authorities over its dealings, while it was forced to close its private banking services aimed at wealthy individuals following concerns over its anti-money laundering safeguards.