* Putin says will open account with Bank Rossiya
* Bank's clients include businesses owned by Gazprom
* Timchenko, also hit by U.S. sanctions, has stake in lender (Adds comments, background)
By Lidia Kelly and Oksana Kobzeva
MOSCOW, March 21 (Reuters) - Russian President Vladimir Putin pledged support on Friday to a secretive bank long-associated with the Kremlin that was hit by U.S. sanctions and which serves clients in Russia's energy sector, including businesses owned by Gazprom.
Bank Rossiya, and its biggest shareholder Yuri Kovalchuk, were included in a new wave of punitive measures by Washington targeted at Putin's close allies over the crisis in Ukraine.
Gennady Timchenko, who also made a list of 20 new names hit by the U.S. sanctions, is another shareholder in the bank. He is one of the founders of Gunvor, one of the world's largest independent commodity trading companies.
Kovalchuk holds a 40.3 percent stake in Bank Rossiya, while Timchenko has 7.9 percent, according to regulatory filings.
Putin, mocking the measures by Washington, played down his association with the bank, but ordered the central bank to support the lender.
"And as for the financial institution (Bank Rossiya): as I understand, it is a medium-sized bank," he told a meeting of Russia's Security Council. "I personally don't have an account there, but I certainly will open one on Monday."
Later he said he would transfer his wages to the bank.
OBSCURE BUT POWERFUL
Little has been known about Bank Rossiya, which has risen to become the country's 15th largest bank by assets last year from 54th in just six years.
Kovalchuk, the largest shareholder in the St Petersburg-based bank is a close Putin ally. The friendship between the two dates back to the early 1990s, when Putin served as deputy mayor of St Petersburg.
Kovalchuk was also one of the three founding members of the Ozero (Lake) luxury dachas complex outside St Petersburg who were targeted by the U.S. sanctions
"Kovalchuk ... Timchenko ... I think I need to stay away from them," Putin joked on Friday.
The bank's operations are concentrated around St Petersburg and Moscow, serving chiefly clients in oil, gas and energy. The bank also controls large insurance firms Sogas and SK Transneft.
The bank, according to its latest financial report, for 2012, served 24,000 corporate clients. Those included a significant portion of Gazprom's businesses, primarily through Gazprom Mezhregiongaz and Gazprom Energy Holding.
"Our companies will continue using the services of the bank," a spokeswoman for Gazprom Mezhregiongaz said on Friday.
According to the bank's most recent balance sheet sent to the central bank, its assets grew by an annual 33 percent as of Oct. 1, 2013 to 401.7 billion roubles ($11.10 billion). The bank's corporate resources base grew by 40 percent during that time to 327.9 billion roubles.
The bank paid 106.5 roubles ($2.94) per ordinary share in dividends on 2012 earnings for a total payout of 267.1 million roubles ($7.37 million), suggesting that Kovalchuk got $1 million in dividends for his stake.
According to a 2008 article by the business daily Vedomosti, nearly 4 percent of the bank belonged to a distant cousin of Putin, Mikhail Shelomov.
One of the bank's clients, the state electricity holding firm InterRAO is run by Kovalchuk's son Boris Kovalchuk.
"We have small rouble deposits and an insignificant loan burden, in both roubles and foreign currency, but settlements for the latter are made in roubles," Anton Nazarov, a representative of InteRAO told Reuters, without disclosing the amounts.
Three of the bank's clients, the utility holdings FSK , Moscow United Electric Grid Co. (MOESK) and the grid company Rosseti, told Reuters they hold only rouble accounts at the bank.
Visa Inc and MasterCard Inc have stopped providing services for payment transactions for clients at the lender and its subsidiary Sobinbank following Washington's sanctions. Western Union the world's largest money transfer company, has also suspended its services for the bank.
"The bank has a strong liquidity cushion and the imposed sanctions will not affect the company's operations," Bank Rossiya said in a statement late on Friday.
"Currently, there is no area (of the bank's operation) that would require assistance from the Central Bank."
The Russian central bank said that it stood ready to support the sanctions-hit bank. "If necessary, appropriate measures will be taken in support of the credit institution and reliable protection of the interests of its depositors and creditors," it said in a statement.
($1 = 36.2354 Russian Roubles) (Additional reporting by Alexei Anishchuk, Anastasia Lyrchikova and Steve Gutterman; Writing by Lidia Kelly; Editing by Pravin Char and Mark Potter)