The index of Russia's Moscow Interbank Currency Exchange (MICEX) slumped 5.5 percent below 1,500 points on Monday, while the RTS stock exchange index dropped almost 8 percent, according to the trading floors.
The indexes fell on the historic decision of international rating agency Standard & Poor's to cut America's top-tier AAA rating.
As of 18:45 pm the MICEX index fell 5.5 percent to 1,499.79 for the first time since October 21, 2010, while the index of RTS sank 7,84 percent to 1,657.77 for the first time since December 10, 2010.
Since Thursday, international stock markets have been falling to their lowest since late 2010, and more losses are feared if governments do not stabilize the euro zone's debt crisis soon and prevent the U.S. economy from sliding back into recession.
The Russian stock market joined the panic on international trading floors on Friday with stock prices slumping an average four percent at open but recovering later.
