On December 15, investors started a massive sell-off of Russia's currency, the ruble. This accelerated depreciation of the ruble, which had been ongoing for several months. In order to stem its further depreciation, the Bank of Russia (Russia's central bank) announced its biggest interest rate hike since 1998, raising a key interest rate from 10.5% to 17%, at an emergency meeting on December 16. Despite this measure, the ruble sharply depreciated throughout the day, falling from 58 rubles per dollar to 80, before rising again to 70. The central bank is currently intervening in foreign exchange markets (meaning it is selling foreign currencies and purchasing rubles) to support the value of the ruble.
The proximate cause of the sell-off was likely a deal announced between Russia's central bank and Rosneft, a major state-controlled oil company, to help cover the company's debts. Many investors viewed the nearly $11 billion deal as potentially inflationary and, given the favorable terms of the deal and the close ties between Rosneft and the Kremlin, a signal that the central bank may not be immune to political pressures.
Depreciation of the ruble will likely exacerbate inflation in Russia. Consumers in Russia are rushing to purchase durable goods, like cars, which are now viewed as more reliable stores of value than the ruble. A weakening of the ruble also raises the value of foreign-currency debt in terms of rubles. The Russian government has relatively little debt, but some Russian corporations are more indebted. High interest rates will likely have severe adverse consequences for Russia's growth prospects.