The Russian Prime Minister, Vladimir Putin, faces more mass protests over alleged election fraud as the former finance minister Alexei Kudrin warned of a ''revolution'' unless the government assuages popular anger.
At least 30,000 people packed Sakharov Prospect, a wide avenue in Moscow named after the Soviet-era dissident Andrei Sakharov, police said. The event organisers said up to 120,000 people attended the rally.
Mr Kudrin, who resigned in September after a clash with the President, Dmitry Medvedev, over military spending, backed opposition calls for the resignation of Russia's most senior election official and their demand for a repeat of the disputed December 4 parliamentary election.
The demonstration, the largest in Moscow since the break-up of the Soviet Union, was a direct rebuff of Mr Putin and Mr Medvedev, both of whom have sought to mollify critics by promising political reforms.
The protesters, who braved below-freezing temperatures and snow, wore white ribbons that have become a symbol of the anti-Putin movement. Some held up signs saying, ''For Russia without Putin.''