* Protesters complain of road blocks
* Protest ahead of March 4 presidential vote
* Organisers, police dispute number of protesters
MOSCOW, Feb 19 (Reuters) - Hundreds of Russians protesting against Vladimir Putin drove through Moscow on Sunday ahead of the March 4 presidential election expected to seal his grip on power.
Cars adorned with white ribbons and balloons, which have become the symbol of the largest protest movement against Putin's 12-year rule, moved bumper-to-bumper through the city, competing with a rally of his supporters hours earlier.
"There are a lot of people who do not agree with the current authorities," said Dmitry, 29, standing next to a red car tied with white ribbons. "We've come out to show ... that we don't agree (with the situation) and want other people to know how many of us there are."
The anti-Putin rallies began after a disputed election in December handed his United Russia party a slim parliamentary majority.
Putin was president from 2000-2008 when he was barred by the constitution from running for a third successive term but has remained in charge as Russia's prime minister. His re-election could see him stay in power until 2024.
A rally of his supporters on Saturday night saw motorists with pictures of Putin and Russian flags stream along Moscow's main ring road. Police said there were 2,000 participants.
Putin's supporters say he led the country out of chaos after the collapse of the Soviet Union and oversaw a rise in living standards during the oil-fuelled boom of his presidency.
Opponents say state workers are pressured to attend pro-Putin rallies with a combination of threats and payments and that police exaggerate the size of the crowds while underestimating the size of opposition protests.
On Sunday, a police official, cited by news agency Itar-Tass, said 150 cars had taken part in the protest calling for fair elections. Organisers, cited by liberal radio station Ekho Moskvy, said 2,000 had participated.
Bundled up against the cold, people stood on overpasses above Moscow's main thoroughfares in solidarity with the drivers, carrying placards that read: "For honest elections".
Sharing pictures on Twitter, protesters complained of closed streets and road works that appeared around the Kremlin on Sunday. Outside the Reuters office, municipal workers had piled snow on a main intersection and worked to remove it throughout the protest.
A similar protest was staged on Jan. 29 when organisers said more than 3,000 motorists took part.
Similar protests were held in other cities, the largest in St Petersburg, according to Ekho Moskvy.
The protests have revealed dismay among Russians, particularly middle-class urbanites, who feel they have no say in politics and that Putin's decision to return to the Kremlin was thrust upon them. (Reporting By Thomas Grove; Editing by Janet Lawrence)