Russian shares fell sharply on Friday as investors weighed the impact of western sanctions over Ukraine. The MICEX index, which is priced in roubles fell 3% and the RTS, which is priced in dollars fell 3.6%. The fall comes after US President Barack Obama on Thursday said sanctions might be extended to key parts of the Russian economy if Russia took further action in Ukraine. Russia's mining, defence and natural resources sectors could all be targets. The country's financial services industry is already under pressure following the introduction of asset freezes and visa bans by the US against high ranking Russian officials. As a result Visa and Mastercard have also stopped providing services to two Russian banks, St Petersburg bank Rossiya and SMP Bank. Bank Rossiya said the card payment services had stopped services for payment transactions for their clients. Visa and Mastercard confirmed they had stopped providing services to SMP Bank without providing notification. 'Frozen' US officials said Bank Rossiya which is linked to a number of Russian businessmen had been sanctioned and would be "frozen" from the dollar. So far banks with connections to high ranking Russian officials have been targeted, but on the stock market shares in other banks have been hit. Shares in Sberbank, Russia's largest bank fell 2.9% while shares in VTB were 4.3% lower. Other sectors were also hit, with gas giant Gazprom down 2.5%, oil firm Lukoil was lower by 3.2%, Russian steel company NLMK fell 2.9% and telecoms firms MTS was down 3%. Shares in gas producer Novatek fell 5.7%. The company is part owned by Gennady Timchenko, a shareholder in Bank Rossiya and one of the wealthy Russian businessmen targeted by western sanctions because of alleged links to President Putin. Negative outlook Ratings agencies S&P and Fitch warned they were changing their outlook for the Russian economy to "negative" from "stable" - the first stage before a possible downgrade in the country's credit rating - because of the potential impact of sanctions. Russia's credit rating is currently BBB. Russian deputy finance minister Alexei Moiseev said he did not see any immediate impact from sanctions on Russia's financial sector or creditworthiness. Meanwhile the rouble was stable on Friday having previously fallen sharply on Thursday evening in response to the announcement of further US sanctions.