Both the European Union and U.S were quick to criticize the vote as against international and Ukrainian law. The specter of economic sanctions loomed as the White House called for "concrete steps to impose costs" on Russia following the referendum.
On Monday, Crimea's government will ask Russia to annex the region, which is part of Ukraine but a key military base for Russia.
"We will await the response from Russia—if they annex markets sell off," Timothy Ash, head of emerging markets research at Standard Bank, told CNBC.
(Read more: Crimeans vote on union with Russia as troops pour in)
Russian stocks and bonds are likely to see a further sell-off this week if the crisis escalates.
Russia's parliament, the Duma, will vote on whether to annex the region on Friday, and it is not a foregone conclusion that they will.There are other options less likely to provoke international opinion, such as keeping Crimea autonomous but maintaining a permanent military presence there.
(Read more: Think US nat gas can threaten Russia? Think again)
European Union foreign ministers will meet Monday to discuss what to do next: whether to impose sanctions like asset freezes or visa bans for Russians and Ukrainians involved in the Crimea: Many of whom are close to Russian President Vladimir Putin.
Germany is likely to be one of the most decisive forces here. It has one of the biggest dependencies on Russian natural gas in Europe, yet Chancellor Angela Merkel, who grew up in Communist East Germany, has been surprisingly strong in her criticism of Russian actions.
(Read more: Ukraine Foreign Minister: We will fight for our land)