"The assignment of the negative outlook reflects the potential for more severe political or economic shocks to emerge, related either to the military conflict in Ukraine or a renewed decline in oil prices, which would further impair Russia's public and external finances," the rating agency said in a press release Friday.
According to the statement, the same factors could drive Russia into a deep recession this year.
Last month, Moody's downgraded Russia's government bond rating to Baa3 from Baa2 with a possibility of a further downgrade. Standard & Poor's (S&P) lowered Russia's sovereign rating from BBB- to a "junk" BB+ with a negative outlook on January 26.
Also in January, international ratings agency Fitch Ratings downgraded Russia's credit rating from BBB to BBB-. All of the agencies cited falling oil prices and ruble depreciation among the reasons behind their downgrades.
Kremlin spokesman Dmitry Peskov has said that the downgrades are politically motivated and do not reflect the real economic situation in Russia.