The speed and breadth of the sanctions overwhelmed years of preparation by Russia after the 2014 sanctions. In a strategy dubbed Fortress Russia, the country built up more than $600 billion in foreign reserves, bought gold and pivoted some exports to China. Closing off Russia’s access to those reserves undercut the strategy, a fact acknowledged by Ms. Nabiullina, the central bank chief.

Timothy Ash, an emerging-market strategist at BlueBay Asset Management, wrote in a note to clients Monday: “From Fortress Russia to Rubble Russia in a week.”

The latest round of sanctions are likely to cause a sizable contraction for Russia’s economy this year, and could prompt bank runs and higher interest rates as the Russian ruble depreciates, according to the Institute for International Finance, a Washington-based global association of financial firms.

Elina Ribakova, deputy chief economist at the IIF, said Monday she expected sanctions to bring about a contraction of at least 10% in Russia’s gross domestic product along with double-digit inflation.