Sweden's financial watchdog is investigating whether buy-now-pay-later (BNPL) fintech Klarna violated bank secrecy laws following a security breach in May.

The Finansinpeltionen (FI) announced the probe following the May 27 incident where users were able to access information on other customers for a limited time.

The investigation will add to ongoing consulation launched in March between FI and Klarna over the latter's information and cyber security practices.

"Bank secrecy is a central part of banks' operations," stated the FI. "Bank customers must know that their information is secure and banks have a major task in always protecting the privacy of their customers."

A spokesperson for Klarna told Reuters that the FI's inquiry "was very much expected as part of our regular dialogue with the Swedish FSA and as always we approach this with full cooperation and transparency".