The White House's measures sent Russian stocks tumbling and weakened the ruble.
LONDON — It was a black Monday for Russian oligarchs as up to $16 billion was wiped off the value of the country's wealthiest tycoons' holdings in the wake of U.S.-imposed sanctions.
The ruble fell to its lowest level against the dollar since late 2016, while shares in sanctioned aluminum producer Rusal, which is controlled by the billionaire Oleg Deripaska, plunged more than 50 percent on the Hong Kong stock exchange.
As Russian stocks tumbled, the Kremlin reportedly said it would step in to support affected companies.
The latest sanctions were announced by President Donald Trump on Friday. They target leading figures close to President Vladimir Putin in an aggressive response to alleged Russian meddling in the 2016 U.S. election.
Bloomberg reported that all but one of the 27 Russian tycoons on its Bloomberg Billionaires Index lost money on Monday. The biggest loser, it said, was nickel miner Vladimir Potanin, whose wealth fell by $2.25 billion.
In total, the net worth of Russia's wealthiest people fell by $16 billion, according to Bloomberg. Forbes Russia said the value of tycoons on its own index fell by $12 billion.
Shares in Sberbank, one of Russia's biggest banks and a barometer of its economic health, fell 17.3 percent.
However, some Russian business leaders remained upbeat. "I lost $250 million in one day," Oleg Tinkov, founder and chair of the board of directors of Tinkoff Bank, told a business conference in Moscow on Tuesday. "But there have been worse days when I've lost $1 billion in a day. So, actually, it was a very positive day."
Putin's spokesman Dmitry Peskov said the Kremlin would back efforts to mitigate the effect of the sanctions package, which he called "egregious in its lawlessness."
"Time is needed for analysis to understand the size of the real damage and to work out steps to correct the situation, for the maximum possible correction," he said Monday.
Prime Minister Dmitry Medvedev ordered officials to draw up measures to support sanctioned companies in the energy, metals and arms sectors, Russian news agencies reported.
Even those companies not under sanctions took a financial hit. Reuters reported that steel miner Evraz was the biggest faller on London's FTSE 100 on Monday, down 8 percent.
Senior U.S. administration officials said that the sanctions were not aimed to punish Moscow for any particular event, but are instead a broader measure aimed at the "totality of the Russian government's ongoing and increasingly malign activities in the world."
However, some experts have warned that trying to squeeze oligarchs is unlikely to bring about a significant change in Putin's policies.
Alastair Jamieson reported from London, and Elena Holodny reported from Moscow.