Moscow police today clashed with small groups of protesters who tried to hold an opposition rally against the election of Dmitry Medvedev as president.
More than 300 police detained dozens of activists, sometimes using batons, and dragged protesters to police buses.
Some of the protesters lit flares spreading smoke across the square in central Moscow, screaming "your election is a farce" and "fascists! fascists!".
Opposition leader Garry Kasparov, the former world chess champion who attended a separate rally in the northern city of St Petersburg, said 250 people had been detained in Moscow.
Western observers have criticised yesterday's presidential election as not fully democratic but Vladimir Putin said the vote was held in strict accordance with the constitution.
Independent opposition candidates were either barred from running or refused to take part in protest.
The meeting was sanctioned by authorities, but a senior opposition activist was arrested before the rally An opposition worker said Maxim Reznik, head of the Yabloko opposition party in St Petersburg, had been detained late yesterday.
Police said Mr Reznik was detained after he had attacked another man.