Updated

Police rounded up scores of people demonstrating against President Vladimir Putin on Sunday, dragging protesters toward buses and beating some who tried to escape.

Hundreds of police armed with shields, body armor and truncheons bore down on demonstrators chanting "Russia without Putin!" in St. Petersburg. Among those detained was a likely contender in next March's presidential election, Boris Nemtsov.

"So many police proves they are afraid of us," Nemtsov told reporters before being taken away. Police said he was released soon after.

It was the second time in two days police have broken up an opposition demonstration in the run-up to Dec. 2 parliamentary elections.

The vote has turned into a plebiscite whether Putin should retain power after stepping down as president next year after two consecutive terms. It isn't clear what formal title he might hold, but he heads the ticket of the dominant United Russia party in the parliamentary elections and has suggested he could become prime minister.

On Saturday, police detained dozens of anti-government demonstrators in Moscow, including former chess champion Garry Kasparov, who was sentenced to five days in prison in a hasty trial.

The Bush administration criticized "the aggressive tactics" of Russian authorities.

"We are troubled that Garry Kasparov and other leaders of the opposition have been arrested and detained," said Gordon Johndroe, spokesman for the White House National Security Council. "We call for them to be given proper access to legal counsel and fair treatment in processing."

In St. Petersburg, police moved in when several young men unfurled signs for the banned National Bolshevik Party as about 100 activists from another party headed to the protest holding white flowers.

Yevgenia Dillendorf, a spokeswoman for the Yabloko party, said the young men with the flags appeared to be provocateurs sent to justify the crackdown. She said 10 parliamentary candidates for Yabloko were among those detained.

Protesters shouted "Shame!" as police seized demonstrators from the crowd and dragged them toward buses. They were seen beating those who tried to escape.

Police said they detained several dozen people.

But Alexander Shurshev, a Yabloko parliamentary candidate who was among those detained, said about 200 opposition activists were rounded up in different parts of the city. Some were held at police stations while others were driven to the city's outskirts and released, he said.

He said he lost consciousness when police hit him over the head with clubs.

Russia's national television stations -- all under state control -- did not cover the demonstrations.

"Russia is again sliding toward dictatorship," said protester Nina Burburova, 73.