MOSCOW -- Moscow police say they have detained at least 400 protesters, including three opposition leaders, at a mass opposition rally
in the capital on the eve of Vladimir Putin's inauguration as Russian president for a third term.
Police clashed with a group of protesters led by Left Front leader Sergei Udaltsov and well-known anticorruption blogger Aleksei Navalny that broke off from a 20,000-strong sanctioned demonstration and tried to march on the Kremlin.
Udaltsov, Navalny, and another opposition leader, Boris Nemtsov, were arrested.
Russian news agencies said that at least 12 riot police were also injured.
Police used megaphones to order demonstrators at the sanctioned demonstration to leave the area and return to their homes before the start of the confrontation.
According to RFE/RL's correspondent in Moscow, Tom Balmforth, some protesters threw projectiles at the security forces.
"Protesters started hurling plastic bottles. Some were even throwing rocks at the police," he said. "And then they started to retaliate and they moved in and basically would brutally beat people with batons and try and move them around, to try and break them up.
"But people weren't really moving and the sheer numbers meant that they could not really get everyone to leave."
There were also reports that police used tear gas against the protesters.
Police cordons were placed around Red Square and other areas leading to the Kremlin.
PHOTO GALLERY: Anti-Putin protests in Moscow
Sergei Mitrokhin, leader of the liberal Yabloko Party, sharply criticized the protesters' breakaway action. He said the conflict with police was "plainly stupid" and that such actions would lead to fewer and fewer participants in future protests.
Mitrokhin told journalists that 90 Yabloko activists had been detained, although none was involved in the breakaway attempt.
"They were taken directly from [the main demonstration] for absolutely no reason," he said.
'March Of A Million'
The unrest came as the opposition was holding a so-called "March of a Million"
to protest Vladimir Putin's May 7 inauguration for a third term as president.
"On the eve of the inauguration of Vladimir Putin, we are gathering to go out and say, 'We don't need an illegitimate government,'" Udaltsov said. "We don't need a so-called government that intends to plunder and destroy Russia for another six years."
Nemtsov also outlined the protesters' demands.
"We are against the Putin mafia group usurping power," he said. "We think it's a tragedy for Russia, that there's no chance of a successful future in the country with this gang.
"We're for honest government in Russia without Putin, for new parliamentary and presidential elections, so that constitutional norms and rules are observed, so that political prisoners are freed."
'The State Is Falling Apart'
Demonstrator Vladimir Lebedev indicated his frustration with corruption under Putin in comments to RFE/RL.
"I am opposed to Putin because the state is literally falling apart," he said. "Corruption is eating away at the entire society. There is no legal system. Of course, there is no rational economic policy. Money is disappearing like water through our fingers into unknown pockets. That's what is happening."
Opposition rallies were also held in other Russian cities on May 6.
In Tomsk, about 150 people marched through the center of the city.
In Vladivostok, six demonstrators were detained and released, with two organizers facing up to 15 days detention for an unsanctioned rally.
A few dozen demonstrators were also reported in Kemerovo.
Meanwhile, several thousand Putin supporters gathered in Moscow's Victory Park in an unsanctioned "celebration." A city official said the group did not need permission because they were holding "a cultural event" rather than a demonstration.
Several independent media outlets, including the newspaper "Kommersant" and the radio station Ekho Moskvy, have reported that their websites are undergoing intense denial-of-service (DOS) attacks.
With reporting by AP, ITAR-TASS, Interfax, and Reuters