Foreign investors in Russia have been served a costly reminder of the political risks of doing business in the country after a week in which a few sentences from Vladimir Putin, the prime minister, helped wipe out half of the value of a New York-listed steelmaker.

Mechel saw its shares plummet after Mr Putin accused Igor Zyuzin, the group’s majority owner, of price-gouging and tax evasion. Before the remarks Mr Zyuzin ranked as Russia’s 12th richest man with a fortune estimated at $11bn. On Tuesday, his worth was about $5.5bn (€3.5bn, £2.7bn).