The central bank of Ukraine issued an alert on April 28 to lenders in the country to review their security procedures after hackers attempted a theft at an unidentified Ukraine bank, according to a confidential message received by Reuters.

The note alleged the incident involved a compromise of the SWIFT messaging system similar to the recent Bangladesh Bank cyber heist, but did not say if the theft was successful.

Hackers had transferred $81 million out of Bangladesh Bank’s account with New York Federal Reserve earlier this year by sending fraudulent messages on the SWIFT network.

The central bank notice, says Reuters, reported that the Ukraine bank incident came to light following SWIFT’s alert to its customers about fraudulent activities on its messaging system.

SWIFT said it is working on improving security and has told banks to improve information sharing.

Read more at Reuters.