People waved homemade signs, with a staggering variety of messages, and many wore the white ribbons that have emerged as the symbol of Russia's "Winter Revolution."
Most said they hadn't come out to support any particular political force or leader but just to express their anger over what they believe was a stolen parliamentary election that returned the United Russia party with a diminished but still dominant 50 percent share of the seats.
More generally, the mostly youthful crowd seemed fed up with the Putin-era system of "managed democracy," which features limited electoral choices, a straitjacketed media and unaccountable, corrupt, and often arrogant authorities.
"We're tired of all the lies, the endless corruption, and feel like we are ready to participate in making decisions," said Vladimir Kuvshinsky, a 30-something network administrator in an IT firm. "We don't want another tyrant, we want a normal government. And we don't want our opinions to be treated like garbage anymore."
Most protesters focused their frustration on Mr. Putin, who has effectively been in charge of Russia for the past 12 years and announced last September that he will seek election as president under the banner of United Russia, which could see him running the Kremlin for another 12 years.
"We don't want 12 more years of Putin's dictatorship," said Ksenia Atarova, who described herself as a writer and critic. "The people have woken up at last, and they want fair elections and a chance to voice their resentment about a lot of things that are happening in this country. We're not going back into the box."