Visa and MasterCard have blocked credit card services to some Russian bank customers as a result of US sanctions.

Four banks are so far affected, all of which have links to Russians blacklisted by the US.

Visa and MasterCard, both US-based companies, are forbidden from having any dealings with those targeted by the sanctions.

The banks, which said card services stopped without warning, have described the move as unlawful.

'Frozen out'.

One of the banks affected, Bank Rossiya, is described by the US as Russia's 15th largest, with assets of $12bn (� 7.27 bn).

The St Petersburg-based bank has been singled out by Washington as the personal bank for senior Russian officials. US officials said it would be "frozen out" from the dollar.

Russian President Vladimir Putin said Bank Rossiya had nothing to do with events in Crimea and promised to transfer his wages there.

Russian President Valdimir Putin.

Russian President Vladimir Putin has promised to protect Bank Rossiya.

"I personally don't have an account there, but I certainly will open one on Monday," he told a meeting of Russia's Security Council.

President Putin also instructed the Russian central bank to step in, if needed, but the latter said the sanctions on Bank Rossiya did "not have a serious bearing on the lender's financial stability".

'Illegitimate'.

Visa and Mastercard also confirmed they had stopped providing services to SMP Bank, which is controlled by US-blacklisted brothers Arkady and Boris Rotenberg.

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Start Quote.

I personally don't have an account there, but I certainly will open one on Monday.".

Vladimir Putin.

Russian President.

The bank, which is Russia's 39th biggest with $5bn in assets, called the actions "illegitimate" because its owners, rather than the bank itself, were the subject of sanctions.

Bank Rossiya's affiliate banks, Sobinbank and InvestKapitalBank, were also affected.

Visa said more than 99 % of its business in Russia was untouched by sanctions.

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 as much as 3 % and the RTS, which is priced in dollars fell 3.6 %.

If Russia took further action in Ukraine, stocks slumped after US President Barack Obama said sanctions might be extended to key parts of the Russian economy.

Share falls.

Russia's mining, defense and natural resources sectors could all be targets.

Stocks recovered some ground during the day after Russian President Vladimir Putin moved to restore calm following the introduction of asset freezes and visa bans by the US against high ranking Russian officials.

The MICEX closed down 1 % and the RTS index was down 1.3 % at the end of the day.

Russia's President Vladimir Putin (R) walks with Russian Railways President Vladimir Yakunin (L) during his visit to a recently constructed train station in Sochi (January 4, 2014).

Allies of the Russian president targeted by US sanctions include railways boss Vladimir Yakunin (left).

Although only banks with connections to high-ranking Russian officials have been targeted, Russian bank shares were broadly lower.

Shares in Sberbank, Russia's largest bank, closed 1.17 % lower - having fallen 2.9 % earlier on Friday, while shares in VTB Bank were 2.61 % lower after falling 4.3 % earlier in the day.

Other sectors were also hit. Gas giant Gazprom was down 0.9 %, oil firm Lukoil ended the day 1.36 % higher. Russian steel company NLMK closed 1.94 % lower.

Shares in gas producer Novatek closed down 9.63 %. The company is part owned by Gennady Timchenko, a shareholder in Bank Rossiya and one of the wealthy Russian businessmen targeted by Western sanctions.

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.

Fitch said: "Since US and EU investors and banks may well be reluctant to lend to Russia under the current circumstances, the economy may slow further and the private sector may require official support.".

Russian businessman Gennady Timchenko.

Gennady Timchenko, owner of gas firm Novatek and shareholder in Bank Rossiya, has been targeted by sanctions.

President Putin's spokesman Dmitry Peskov criticised the move, suggesting it was not an objective decision and that somebody "ordered" it.

Russia's credit rating is currently BBB.

Meanwhile the rouble was stable on Friday having previously fallen sharply on Thursday evening in response to the announcement of further US sanctions.

Later on Friday morning Germany said it had decided to suspend approval of all defence-related exports to Russia.

Berlin ordered defense contractor Rheinmetall to halt delivery of combat simulation gear to Russia earlier this week.

The ministry spokesman said this was a "one-off" case, but future deals would also be blocked.

"The (Rheinmetall) case that you are talking about is a one-off case. It is true that given the current situation in Russia, we are notapproving any exports of defense goods to this country at the moment," the spokesman said.