The police action did not prevent more than 2,000 people from gathering in a central square, where leftist and liberal groups demanded that Russian President Vladimir Putin stop what they called Russia's retreat from democracy.
"In 15 months political power will be changed," said Mikhail Kasyanov, a former prime minister who is now an opposition leader, referring to the March 2008 presidential election.
"Next year everyone should make a personal decision about what to do with our country _ whether we allow these people to continue their illegal undertakings ... or we finally make our main goal to build a democratic and socially oriented state," Kasyanov told demonstrators.
Garry Kasparov, the former chess grand master who has emerged as one of the Kremlin's most prominent critics, said the mere fact that the rally took place made it a success, given the efforts by authorities to stop it.
"We are protesting and it means that authorities are not as monolithic and powerful" as they believe, he said. "They are afraid that one day we will tell them 'enough.'"
The demonstrators chanted "Freedom" and held banners reading "No to Police State" and "Russia Without Putin."
Since he took office in 2000, Putin has taken steady, gradual steps to centralize power and eliminate democratic checks and balances.
He has created an obedient parliament, abolished direct gubernatorial elections, tightened restrictions on rights groups and presided over the elimination of most opposition voices from the media, especially the television networks.
The demonstration, organized by the Other Russia movement and other opposition groups, had originally planned to march down a main Moscow avenue. City authorities banned the march, allowing only the rally.
Organizers had vowed to conduct the march in defiance of the ban. But Natalya Morar, spokesman for Other Russia said police and defense troops had sealed off Triumfalnaya Square _ the scene of the protest _ and lined the avenue.
An AP photographer saw more than 1,000 law enforcement officers in full riot gear, some with police dogs, cordoning off the Triumfalnaya Square. Moscow residents complained the city was flooded with police and troops.
About 80 protesters, including Ivan Starikov, a senior member of the liberal Union of Right Forces, were detained in Moscow throughout the day, many of them without any explanation, Morar said.
About 320 other opposition activists were detained or taken off trains and buses on their way to Moscow, she said. Some were kept in detention cells, she said, while others were released after the rally was over.
Yevgeny Gildeyev, spokesman for the Moscow police said some 8,500 law enforcement officers were deployed in the city on Saturday. He said he did not know how many opposition activists were detained.
Russia's often fractious opposition has faced increased harassment in recent years, especially after protests led to the toppling of governments in the former Soviet states of Georgia and Ukraine.
Authorities have banned meetings on dubious legal grounds, while party congresses have been broken up or canceled for no reason.
-- Michael Pugliese