"The Financial Supervision Authority launched a sanction proceeding on October 28 to investigate the signs of money laundering fraud in Swedbank's financial supervision proceedings," the FSA said in a statement.

"As the inspection revealed signs of a criminal offence, the Financial Supervision Authority decided to abandon sanction proceedings in favour of criminal proceedings."

Swedbank did not immediately respond to a Reuters' request for comment.

Late last month, Estonia's state prosecutor's office said it had launched a criminal investigation into Swedbank over alleged money laundering between 2011 and 2017.

The financial regulator said it would cooperate with the prosecutor in the criminal investigation.

Earlier this year, a report by Sweden's public broadcaster SVT alleged that money laundering could have occurred in transactions between Swedbank and Danske Bank in the Baltics between 2007 and 2015.

Danske is being investigated in five countries over some 200 billion euros ($226 billion) of suspicious payments from Russia, ex-Soviet states and elsewhere that were found to have flowed through its Estonian branch.

Danske and Swedbank have previously admitted to failings in their money laundering controls in the Baltics.

(Reporting by Tarmo Virki. Editing by Simon Johnson and Carmel Crimmins)