In his brief assessment on the impact exclusion from SWIFT would have on Ukrainian banks, hedge fund billionaire Bill Ackman said that "once a bank can't transfer or receive funds from other banks, its solvency can be at risk. If I were Russian, I would take my money out now. Bank runs could begin in Russia on Monday."

He may have been off by one day, because in the hours following the western announcement to suspend some Russian banks from SWIFT and to launch sanctions on the Russian central bank, we have seen scenes across Russia reminiscent of a bank run as locals lined up at cash machines around the country to withdraw foreign currency amid growing fears the ruble could collapse when it resumes trading on Monday.

"I've stood in lines for an hour, but foreign currency is gone everywhere, just rubles," said Vladimir, a 28-year-old programmer who declined to give his last name, while waiting in a long line at an ATM in a Moscow shopping mall. "I got a late start because I didn't think this was possible. I'm in shock."

There are indications that the ruble will fall sharply when trading opens on Monday. Exchange rates being offered by lenders are already varying widely on Sunday, from 98.08 rubles per dollar at Alfa Bank to 99.49 at Sberbank PJSC, 105 at VTB Group and 115 at Otkritie Bank at 3:30 p.m. in Moscow. The spot ruble price on the Moscow Exchange closed at 83 per dollar on Friday.

"I can't see a scenario where it doesn't get hammered," said Paul McNamara, a fund manager at GAM Investments. "I don't expect effective intervention in terms of pricing, but in terms of reducing legal grounds to sell rubles."

The rush for foreign currency came despite Bloomberg reporting that some lenders selling dollars at more than a third higher than the market's close on Friday, and well past the psychologically important level of 100 rubles per dollar that many economists said would trigger an interest-rate hike by the Bank of Russia. The shock came as Russians were still digesting news that Europe was closing its airspace to them and popular payment systems like ApplePay would stop working.