Thousands of Russians have rallied in Moscow and other cities to challenge Vladimir Putin's victory in Russia's presidential election, prompting hundreds of arrests.
Police said they had arrested 250 people in Moscow and 300 in Saint Petersburg on Monday after moving in roughly to break up demonstrations against what opposition activists say was a rigged vote.
About 20,000 anti-Putin protesters turned out in Pushkin Square in central Moscow chanting "Russia Yes! Putin No!".
The opposition supporters, who had been granted permission by authorities to protest for an hour, gathered in front of a stage emblazoned with the slogan "For fair elections".
Al Jazeera's Christopher True, reporting from the square, said: "After the allotted time for the demonstration was up, there was some heavy-handed tactics by police to clear the area.
"Officers formed rings and herded protesters down into the entrances of the Moscow metro. Dozens of people were arrested, including some of the main opposition leaders at the event."
Putin, who has dominated Russian politics since the beginning of the 21st century, won more than 63 per cent of Sunday's vote, according to the nearly complete official returns, but the opposition has alleged widespread fraud and independent monitors said the vote was skewed in Putin's favour.
Monitors from the Organisation for Security and Co-operation in Europe (OSCE) pointed at the lack of real competition in the race and said the vote count "was assessed negatively" in almost a third of polling stations observers visited.
Criticism of the vote has added fuel to protests by Putin's critics who are questioning his victory and demanding an end to his dominance of the Kremlin.
The Pushkin Square rally followed a series of massive previous demonstrations against Putin's rule. A protest planned by the opposition group, Solidarity, was stopped by riot police who bundled participants into waiting buses.