The theft of $13 million from ATMs in Japan using counterfeit cards from South African lender Standard Bank prompted a call for vigilance from South Africa's central bank on Wednesday.
Thieves made 14,000 withdrawals in just three hours - 78 a minute - from bank machines at 7-Eleven convenience stores across Japan, according to a source familiar with the matter.
Central bank deputy governor Kuben Naidoo told reporters that Standard Bank would shoulder the losses.
"We are pleased that Standard Bank publicly said what had happened. We don't know all the details yet but we're looking into it and we will take all the steps necessary to protect our payment systems and banking systems from similar types of attacks," he said.
"We are working with the banks to ensure that they are constantly upgrading their ability to detect and repel cyber attacks. But you will always be subjected to these attacks."
Standard Bank said on Monday it had suffered the losses, not its customers, and that it had alerted the authorities. It estimated its total loss at 300 million rand ($19 million).
The bank has declined to comment further.
The thieves are still at large. Japan's Mainichi newspaper citing sources reported that police suspect more than 100 people were involved in the theft which took place on May 15, a Sunday, in Tokyo and across 16 prefectures.
Most ATMs in 7-Eleven stores belong to Seven Bank, a Japanese lender part-owned by Seven & I Holdings which operates the store chain in Japan. It is one of only two Japanese banks that allow withdrawals on foreign cards.
Experts said both banks should shoulder some blame for failing to monitor the flood of transactions, saying they should have had systems in place to detect unusual activity.
($1 = 110.0600 yen)
(Reporting by Nqobile Dludla; writing by James Macharia; editing by Jason Neely)