"We are affirming our 'BB+/B' long- and short-term foreign currency ratings and our 'BBB-/A-3' long- and short-term local currency ratings on Russia," the ratings agency said in a statement.
"The outlook remains negative, reflecting our view that we could downgrade Russia if external and fiscal buffers deteriorate over the next 12 months faster than we currently expect."
The ratings agency warned it could lower the ratings furthermore if Russia's monetary policy flexibility continued to diminish.
In 2014, Russia was hit by an economic downturn amid a dramatic drop in oil prices on global market and Western economic sanctions imposed against Moscow over the Ukraine crisis.
Although the Russian ruble had lost almost half of its value in 2014, it began to stabilize following the start of 2015.
Russian President Vladimir Putin said Thursday during a Q&A session in Moscow that Russian economy may rebound within the next two years.