Ruble's slide adds pressure to Russian economy amid plunging oil prices, sanctions

"I don't think the central bank can do very much to help the situation. It can stabilize slightly, but the fundamental problem is bad economic policy, falling oil prices and financial sanctions from the West," he said, noting that the Russia's economy remains hugely reliant on energy, as oil accounts for half of federal government revenue and two-thirds of its total exports.

Tran also warned that "any one single measure by the Russian central bank" will not be sufficient to reinforce investors confidence in the ruble, unless oil prices start to rebound, financial sanctions could be rolled back and the Russia's economy begins to recover.

Sharp currency depreciation cost Russian firms dearly, which earn in rubles but need to repay debt in dollars and other foreign currencies. Western sanctions and geopolitical uncertainty have almost blocked access of Russian financial institutions and firms to international capital markets.

"It has turned out that the financial sanction has been very effective, far more effective than almost anybody thought at the beginning. So nobody today is prepared to give Russia any financing," Aslund noted. "Everybody is afraid of US financial regulators. They are very careful not to do anything that can be considered to break financial sanctions."

Experts said Russia's economic outlook hinges mainly on Western sanctions and oil prices. "Any progress or lack of progress on Ukraine in the next few weeks or months will be important to see whether these sanctions will be softened or new sanctions will be applied. That will be very important to assess the economic outlook for Russia," Tran said.

If oil prices stay at around 60 dollar a barrel for a long period, falling by about 50 percent since June, Tran expected Russia's Gross Domestic Product (GDP) to decline by four to five percent next year, echoing Russian central bank's forecast of a 4. 5 to 4.7 percent contraction.

Aslund was more pessimistic, saying "Russia is going to face a significant period of severe economic situation." He estimated that Russia's export revenues will fall by 30 percent and imports will decline by 50 percent next year. Inflation will rise further above 10 percent and GDP will contract by 5 to 10 percent, he said.

While admitting the adverse impact of Western sanctions on the Russian economy, Russian President Vladimir Putin said earlier in his annual press conference that it would take at most two years for the Russian economy to rebound under the most unfavorable scenario.