Social networks and a new civic group called the League of Voters had encouraged motorists and other critics of Prime Minister Vladimir Putin and his effort to retake the presidency to display a white ribbon or other symbol and travel Moscow's Garden Ring, a circular avenue around downtown.
Follow RFE/RL Russian Service's live reporting of the event, which kicked off at 2:00 p.m. local time
Organizers of the "carousel-style" protest -- in which individuals avoid massing in one place at one time to avoid assembly bans -- pronounced victory in their effort to attract around 2,000 vehicles, RFE/RL's Russian Service reported.
They described the event as having "locked the ring."
Backers claimed that some 3,000 cars joined the protest, while police said they numbered more like 300.
Kremlin gadfly and anticorruption blogger Aleksei Navalny and opposition leader and former Nizhny Novgorod Governor Boris Nemtsov participated in the action.
An RFE/RL correspondent said pedestrians and passing cars displayed white ribbons and balloons and waved scarves and other objects to symbolize the goal of "pure" elections.
Watch a video of motorists adding white objects to their vehicles to show support for democratic elections (in Russian)
The December 4 elections for a new State Duma sparked street demonstrations that have been unprecedented since Putin assumed the presidency in late 1999.
Forced under the Russian Constitution to step down in 2008 after two consecutive terms, Putin remained the country's most powerful politician as prime minister and is the favorite to win the March presidential vote.
Critics at home and abroad say his carefully orchestrated power swap with current president and Putin protege Dmitry Medvedev, who isn't seeking a second term, could spell political and economic stagnation.
The creation of the League of Voters by leading journalists, activists, and other personalities angry at perceived abuses was announced earlier this month.
written by Andy Heil based on RFE/RL Russian Service reporting