The United States has expanded sanctions against Russia. Washington has imposed sanctions on Russian businessman Vladimir Potanin, one of Russia's richest men, as well as his wife, adult children, a yacht and Interros, the investment holding company controlled by Potanin, according to a State Department press release.

Potanin, 61, is the largest shareholder in Nornikel, which has not been sanctioned. "Interros owns 36% of Nornikel.

Nornickel is the world's largest producer of palladium and refined nickel.

The U.S. Treasury Department said Washington also imposed sanctions on Rosbank as well as 17 subsidiaries of Russia's VTB, which was listed by Washington earlier this year.

The State Department also imposed sanctions on members of the board of directors of Russian Railways, members of the government, including the governor of the Moscow Region, and members of their families.

It also imposed sanctions against seven Russian-appointed proxies in Ukraine, the State Department said in a statement.