Some youthful members of the National Bolshevik Party, a banned radical youth group that specializes in theatrical anti-Kremlin protests, unfurled their hammer-and-sickle flag and lighted flares. The group is headed by Eduard Limonov, a writer criticized by some for having a nondemocratic ideology. Kasparov and former Prime Minister Mikhail M. Kasyanov have said that their alliance with him is justified by a need to unite all anti-Kremlin forces to keep hope for democracy alive.
When the crowd had walked about half a mile, hundreds of riot police officers moved in, mostly going after young people and those with flags or banners, grabbing them roughly and putting them on police buses. People with cameras were also targets, although most journalists who could produce accreditation cards were released on the spot. Some middle-aged and elderly protesters also were detained.
Reuters news agency reported that four of its journalists -- two photographers and two camera crew members-- were detained as they covered the protest. They were later released without being charged, it said.
Police said they detained about 250 demonstrators, the Russian news agency RIA Novosti reported.
About 1,000 protesters eventually gathered at the approved site to hear speeches, including one by Kasyanov, who served during Putin's first presidential term but joined the opposition after being dismissed from office three years ago.
"There are no free elections. There is no respect for people," said Kasyanov, a potential opposition presidential candidate in balloting next year, when the constitution requires that Putin step down.
"The authorities are afraid of free people. They're not afraid of slaves and obedient people. But they're afraid of you."
Times staff writer Sergei L. Loiko contributed to this report.