New US sanctions against Russia that were announced Thursday target a bank so closely identified with President Vladimir Putin's inner circle that its chairman is widely known as "Putin's banker." Washington slapped business bans and asset freezes on Bank Rossiya and chairman and main shareholder Yuri Kovalchuk, to pressure Moscow over its annexation of Ukraine's Crimea region. Also targeted were top businessmen close to Putin -- billionaires Gennady Timchenko, Arkady Rotenberg and Boris Rotenberg. The sanctions mean Americans and American businesses are forbidden from any business dealings with them and that any assets they might have in the United States are frozen. The US Treasury called Rossiya, Russia's 17th largest bank, "the personal bank for senior officials of the Russian Federation." It said the bank, with assets of around $10 billion, especially serves the oil, gas and energy sectors and that Kovalchuk acts as the "personal banker" for top Russian officials. "Kovalchuk is a close advisor to President Putin and has been referred to as one of his 'cashiers'," it said. Earlier this month, Forbes magazine put Kovalchuk's net worth at $1.4 billion through a stake in the bank and insurance subsidiaries, six Russian television channels and wireless operator Tele2 Russia. Forbes ranked oil and gas tycoon Timchenko as Russia's sixth richest man, with a $15.3 billion fortune from Geneva-based commodity trading house Gunvor. The Rotenbergs allegedly received $7 billion in contracts on Putin's orders for the Sochi Olympic Games, and more from the state energy company Gazprom, according to the Treasury. "Both brothers have amassed enormous amounts of wealth during the years of Putin's rule in Russia," it said.