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.