Russia's main stock exchange halted dollar and euro trades on Thursday after the United States hit Moscow with a new package of sanctions over its military offensive in Ukraine.

Washington announced Wednesday it was sanctioning Moscow Exchange, Russia's main stock market and clearing house for foreign currency transactions, a major new financial punishment.

"Due to the introduction of restrictive measures by the United States against the Moscow Exchange Group, exchange trading and settlement of instruments in US dollars and euros will be suspended," Russia's central bank said in a statement Wednesday evening.

Measures that target Russians' ability to buy and trade foreign currency typically provoke a strong reaction in Moscow and throughout Russian society.

The exchange rate is seen as a key indicator of the health of the Russian economy.

Russians will still be able to trade in dollars and euros outside of the centralised Moscow Exchange -- something which could limit liquidity and lead to higher volatility.