Russia's central bank says that hackers stole more than two billion rubles (around $31 million) from correspondent accounts this year.
Targeting accounts held with the central bank by commercial banks, the crooks tried to steal five billion rubles but some of the money was saved, a spokesperson told CNN.
Details of the attacks are scant, but according to Reuters the thieves faked client credentials, echoing the recent spate of hits on the Swift messaging network.
The most famous of these saw crooks steal $81 million from the Bangladesh central bank's account with the New York Federal Reserve by sending wire transfer requests over Swift.
Meanwhile, Russia is also accusing foreign spy agencies of trying to disrupt its banking system with cyber attacks and social media propaganda.