Dozens of opposition activists were detained by riot police today as they tried to rally against Russian President Vladimir Putin's government in central St Petersburg.
Boris Nemtsov, an opposition leader and a likely contender in next March's presidential election, was among scores of protesters detained by authorities.
Riot police with helmets, shields and body armour moved against demonstrators who gathered near the State Hermitage Museum, chanting "Russia without Putin".
"What we are seeing now in St Petersburg resembles a military operation," said Olga Kurnosova, a co-ordinator of the Other Russia coalition of opposition groups that organised the rally. "It shows the authorities' fear."
The police action came one week before December 2 parliamentary elections, and a day after police detained anti-government demonstrators, including the former chess champion Garry Kasparov, after a rally in Moscow.
Police moved in when young protesters unfurled banners of the banned National Bolshevik Party as about 100 activists with white flowers headed from the Yabloko party headquarters to a planned rally against Putin's government.
Police detained the young marchers first and then about several dozen other protesters, an Associated Press reporter witnessed.
Yabloko activist Daria Makukhina said that several party activists running for parliament in next Sunday's vote were beaten and detained.
When several hundred demonstrators reached the Dvortsovaya Square in front of the museum, they found it tightly blocked by riot police.
Police then began rounding up protesters, detaining more than 100, including Mr Nemtsov, one of the leaders of the Union of Right Forces party.
Other protesters shouted "Shame!" as police picked up demonstrators from the crowd and dragged them toward buses.
Mr Nemtsov's party and other opposition groups have complained of being hobbled during the election campaign by official harassment.
The Kremlin has mounted a major campaign to produce a crushing victory for Putin's United Russia party in December 2 parliamentary elections - perhaps to ensure that Putin can continue to rule Russia even after he steps down as president in May.
The constitution prevents him from serving three consecutive terms.