As of 18:45 Moscow time, Russia's dollar-denominated RTS stock exchange fell 8.61 percent to 1,387.86 and the ruble-denominated MICEX index dropped 7.82 percent to 1,389.43.
On Wednesday, the Federal Reserve rattled investors with the statement that the U.S. economy faced significant downside risks, and analysts worried that fresh measures to kick-start growth would be insufficient.
The Fed also launched a $400 billion operation to lower borrowing costs for U.S. businesses and consumers and boost the economy, selling its shorter-term securities to buy longer-term holdings.
In Europe, France's CAC 40 index fell 4.49 percent to 2,804.12, Britain's FTSE 100 by 4.27 percent to 5,062.50, Frankfurt's DAX by 4.72 percent to 5,177.42, as of 18:55 Moscow time.
The official exchange rate of ruble plunged to a two-year low as prices for Russia's main export item, oil, fell over three percent on Thursday.
