MOSCOW — Russia has a new enemy: the currency markets.

Russia’s government is in the middle of an all-out fight to preserve the value of the ruble in the face of plummeting oil prices and Western sanctions over the Ukraine crisis. In the boldest move yet to stanch the bleeding, the Central Bank of Russia announced a stunning interest rate increase in the middle of the night.

Its main deposit rate is now 17 percent, up from 10.5 percent when Russian banks closed for business on Monday. The rate increase, one of the largest ever announced by the central bank, echoes the drastic measures taken during the 1998 crisis when Russia defaulted on its debt and devalued the ruble.

The question is whether the move — announced on the central bank’s website at 1 a.m. in Russia — will appease the markets. If it doesn’t, investors may view the rate increase as a sign of increasing disarray.

Some economists are concerned that Russia is now stuck in the quagmire of stagflation, or high inflation and low growth. The government expects inflation of 10 percent or more by the end of this year and for the country to fall into a recession next year.