Payeer allowed Russian customers to carry out transactions in Russian roubles to and from EU-sanctioned Russian banks, according to Lithuania's Financial Crimes Investigation Service (FNTT).
Russian individuals and legal entities were also offered the chance to receive crypto wallet, account management and storage services, says the FNTT.
Over a period of around 18 months, Payeer had at least 213,000 customers, and the company's revenue reached more than EUR164 million.
In a statement, the FNTT says "the identities of the company's customers were not properly determined and checked intentionally, in order not to lose a significant part of the income".
Payeer - which set up in Lithuania after its license in Estonia was revoked - has been fined EUR8.2 million for the sanctions violations and another EUR1.1 million for related AML failings.