Some of Russia's richest men have been forced into a firesale of assets as tough market conditions make it difficult for them to repay Western and local lenders.

Many oligarchs borrowed heavily to build their empires and when Russian share prices were rising, they used shares in their companies as collateral for these loans. The recent turmoil in world stock markets has led to a succession of margin calls and some Russian billionaires have found that the value of their collateral no longer covers their debt and they have been forced to sell assets to repay lenders.

Oleg Deripaska, thought to be Russia's richest man, was forced to give up his $1.5 billion (£889 million) investment in Magna, a Canadian car parts company, last month. He lost about $500 million when he was forced to sell a 9.9 per cent stake in Hochtief, the German infrastructure company.

Last week, Russia's central bank said that Russian companies would have to repay about $47.5 billion to foreign creditors this year and a further $160 billion next year.

Fears that large stakes in Russian companies could fall into the hands of Western bankers has prompted speculation that state-controlled banks could bail out the oligarchs. VEB, the Kremlin-backed bank, is rumoured to be prepared to back Mr Deripaska in refinancing his 25 per cent stake in Norilsk Nickel. RusAl, the oligarch's company, bought the stake this year for $13 billion, after borrowing $4.5 billion from banks including Goldman Sachs and Morgan Stanley. The value of the stake has fallen to $2.34 billion.

Mr Deripaska must refinance $2 billion of the loan by the end of this month and may need the help of the Kremlin to do so. VEB may also have to bail out Vladimir Lisin after the value of Novolipetsk Steel fell by about $11 billion after a 75 per cent drop in its share price. Yevgeni Chichvarkin, of Euroset, Russia's largest mobile phone retailer, was not bailed out by the State and sold Euroset at a fraction of its value.

Other Eastern-bloc billionaires have faced similar problems. Kostyantin Zhevago, of Ukraine, sold a 25 per cent stake in Ferrexpo, the iron ore producer, after his lenders made a margin call on the shares.

Times Recommends

• Lies and cover-up at MG Rover exposed by report
• High oil prices push manufacturing costs up
• Primark founder steps down as chief executive