Russian President Vladimir Putin has urged a gathering of Russia's billionaires and business leaders to return their capital to Russia and suggested that funds kept abroad could be frozen.

In an apparent reference to the possibility of further U.S. and European Union sanctions on Russia for its involvement in the Ukraine crisis, Putin warned of a possible "limit on the use of these capital amounts which are located in foreign jurisdictions."

Citing "disturbing information from a number of countries," Putin told the conference in Moscow that measures could be introduced to prevent capital being returned to Russia.

Faced with record capital flight of $151.5 billion last year, Putin proposed a capital amnesty in December, under which funds brought back to Russia would not face questions on tax and other issues.