MOSCOW—Want to use virtual bitcoins in Russia? You had better be careful, otherwise you may find yourself involved in a real-life crime, the Bank of Russia said Monday.

Introduced in 2009, bitcoins first drew little attention but then became an increasingly popular digital currency to carry out electronic transactions across the globe. German Gref, who chairs Russia's largest lender Sberbank, said late last year that his bank may issue electronic money such as bitcoins together with Russia's leading search engine Yandex at...