Anti-Kremlin demonstrators plan to take to the streets of St Petersburg, a day after a rally in Moscow ended in scuffles and arrests.
During yesterday's opposition march in the capital, 170 people were arrested, including activist and former chess champion Garry Kasparov.
Protesters, allied under the Other Russia coalition, said the tough reaction to the Moscow march would boost the turnout at the rally in Russia's second-largest city.
More than 9,000 police were deployed to prevent protesters from gathering at Pushkin Square yesterday.
The huge security operation came as Russia said it wanted the extradition of London-based exile Boris Berezovsky, who had told the Guardian newspaper that he was plotting 'revolution' to overthrow Vladimir Putin.
