(Bloomberg) -- South Korea’s Financial Supervisory Service is probing $3.4 billion worth of “abnormal” foreign-exchange transactions at two of the country’s largest commercial banks for possible links to illegal crypto-related activities. 

Unusual transactions totaling 1.6 trillion won ($1.3 billion) took place at five branches at Woori Bank between May 3, 2021 and June 9, 2022, the regulator said in a statement Wednesday. Similar transactions worth 2.5 trillion won were detected at one of Shinhan Bank’s branches between February 23, 2021 and July 4, 2022, it said. 

Yonhap reported last week that the two banks were involved in unusual transactions worth 1.8 trillion won. Financial regulators have been looking into whether the transactions had links to money laundering or currency speculation using crypto assets. Some of the transactions involved crypto exchanges, a senior FSS official said last week.

The FSS on July 1 required all banks to conduct an internal review on all sizable overseas transfers as well as any suspicious transactions related to cryptocurrencies that occurred in 2021 and the first half of this year, the statement said. The banks will need to submit a report by end of July.

The information will be shared with the nation’s tax office and the prosecutors office, the FSS said.

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