The exchange and the central bank rushed out statements on Wednesday - a public holiday in Russia - within an hour of Washington announcing a new round of sanctions.

"Due to the introduction of restrictive measures by the United States against the Moscow Exchange Group, exchange trading and settlements of deliverable instruments in USD and euros are suspended," the central bank said.

The move means banks, companies and investors will no longer be able to trade either currency via a central exchange, which offers advantages in terms of liquidity, clearing and oversight.

Instead, they will have to trade over-the-counter (OTC), where deals are conducted directly between two parties. The central bank said it would use OTC data to set official exchange rates.

Many Russians hold part of their savings in dollars or euros, mindful of periodic crises in recent decades when the rouble has crashed in value. The central bank reassured people that these deposits were secure.

"Companies and individuals can continue to buy and sell US dollars and euros through Russian banks. All funds in US dollars and euros in the accounts and deposits of citizens and companies remain safe," it said.