“More than 300 people have been arrested,” the agency quoted the police press office as saying. Among those detained was popular anti-corruption blogger Alexei Navalny, it said. Navalny had earlier tweeted that he was “sitting in a (police) bus.”

The Gazeta.ru website said about 5,000 people gathered under pounding rain in central Moscow at a protest featuring liberals who had been barred from participating in the polls.

“Today is a historic day for Russia. Putin and his party are thieves and those swindlers have lost in a shameful manner,” said Vladimir Ryzhkov from the opposition movement Parnas.

After the rally, hundreds tried to march on to the election commission but police blocked them.

Police said about 100 opposition protesters were also detained in Russia’s second city of Saint Petersburg after they tried holding an unsanctioned rally on the main Nevsky Prospekt thoroughfare for the second day in a row.

Prime Minister Putin’s United Russia collected just 238 seats in the 450-seat State Duma in Sunday’s election, down sharply from the 315 seats it won in the last polls in 2007.

The vote was marred by unprecedented state pressure against independent election monitors and various reports of violations that drew a stiff rebuke from a group of European observers led by the OSCE.