Mr Browder's complaint, filed by his Hermitage Capital Management, called on Latvian authorities to look into the allegations alongside their ongoing broader probe into Russian money laundering links.

Latvia's Financial Intelligence Unit told Reuters it does not comment on such cases. The Economic Crime Combat Department of the Latvian Police, meanwhile, confirmed it had received a letter from Mr Browder and would assess the information contained within it, but otherwise declined to comment.

"We cooperate with the authorities in all our home markets in order to resolve current issues," spokespeople for Swedbank said in an emailed response. "However, we have no comment on the specific cases that Bill Browder now points to."

On 4 March, Mr Browder filed a report of criminal conduct against Swedbank in Sweden, but a prosecutor of the Swedish Economic Crime Authority reached the conclusion that an investigation would not be launched.

Billions of dollars involved

Last July, Mr Browder sought for a criminal investigation to be launched against 26 employees of the Estonian branch of Danske Bank who allegedly enabled the laundering of billions of dollars of dirty money through the bank.

According to the complaint, the content of their activity to a great extent included creating opportunities for money laundering, aiding money laundering, and the concealment of this activity, which involved at least 190 different bank accounts. The volume of transactions passing through 21 of these accounts exceeded altogether $9 billion.

Hermitage Capital's investigation has since reached the conclusion that money moved from Danske's Estonian branch and Lithuania's Ūkio Bankas to bank accounts at Swedbank Estonia. According to Mr Browder's statement, $14.2 million moved from Danske to Swedbank, and $102.7 million from Ūkio to Swedbank.

Swedish public broadcaster SVT reported in February that Swedbank customers were able to funnel at least 40 billion kronor, or €3.8 billion, between Swedbank and Danske Bank in Estonia.