Russia urged companies to delist their shares from overseasstock exchanges and trade in Moscow in an effort to safeguard themas international sanctions mount against the country after itstakeover of Crimea.

“This is a question of economic security,” First Deputy PrimeMinister Igor Shuvalov told reporters after a government meetingnear Moscow today. Speaking later in a telephone interview, he saidthe move isn't mandatory and that companies should make independentdecisions.

The U.S. and Europe are threatening to step up economicsanctions against Russia following President Vladimir Putin's moveto annex Crimea from Ukraine last month. Higher borrowing costs ledthe government to scrap ruble-bond auctions in five of the last sixweeks. Since the incursion into the Black Sea peninsula on March 1,investors turned to offshore equity trading, with U.K. volumegrowing faster than in Moscow.