Thousands of protesters flocked to a central Moscow avenue today to demand Vladimir Putin's resignation and protest electoral fraud.

The rally had been widely seen as a test of whether the opposition is able to maintain its strength after Prime Minister Putin won a return to the Kremlin.

Putin, Russia's president in 2000-2008, had to step down in 2008 to avoid the terms' limitations. He won 64% of the vote last Sunday and is set to stay in the Kremlin for the next 6 years.

Although violations at the presidential vote were numerous, observers, however, viewed the vote as fairer compared to the December parliamentary vote.

But the protesters do not recognise the vote's results. "These weren't elections. This isn't a president," read a banner on the stage.

"I don't believe that this election was fair," 18-year-old student Elizaveta Chernysheva said. "There have been a lot of falsifications."

City authorities have given permission for a rally of up to 50,000 on the pavement of a central Novy Arbat avenue which is part of the route used by high-speed motorcades that whisk top figures to and from the Kremlin.

Rallies protesting the widely reported fraud in the parliamentary election have attracted up to 100,000 people in the largest display of discontent in Russia's post-Soviet history.

Last Monday, the day after the election, Moscow police arrested some 250 people who stayed on a central-city square after the time authorised for a protest rally ran out.