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Standard Bank says its South African banking operations of the have been the victim of a sophisticated, coordinated fraud incident.
It says in a statement on Monday morning that this involved the withdrawal of cash using a small number of fictitious cards at various ATMs in Japan.
The target of the fraud has been Standard Bank and there has been no financial loss for customers.
Standard Bank says it has taken swift action to contain the matter and the gross loss to the bank is estimated at R300m.
This is prior to any potential recoveries that may serve to reduce the loss.
The bank says the relevant authorities have been alerted. It says investigations are at a sensitive stage and further information will be provided as appropriate.