[bold]As much as $30bn (£20bn) has been stolen in preparations for next year's Winter Olympics in Sochi, Russian opposition leaders say.[/bold]
Boris Nemtsov and Leonid Martynyuk say the games are "a monstrous scam" and will be the most expensive in history, costing more than $50bn.
A lack of fair competition and secrecy sharply increased the cost, benefitting only businessmen close to President Vladimir Putin, they say in a report.
A Russian official dismissed the claim.
Mr Nemtsov was quoted by Reuters as saying that he would now be pushing for a thorough investigation into the matter by Russian prosecutors.
He also questioned the wisdom of staging the games in a subtropical climate in the city on the Black Sea coast.
But Deputy Prime Minister Dmitry Kozak, who is responsible for the 2014 Games, was quoted as saying: "In spite of envious people, the Russian Winter Olympic Games will be held in the southern capital - subtropical Sochi."
Meanwhile, International Olympic Committee (IOC) spokesman Mark Adams said it appeared that Russia was taking any corruption claims related to the Olympics seriously.
Mr Adams said Moscow was addressing the issue "pretty much head-on from the president down", according to the Associated Press news agency.
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