Thousands of protesters angry over the impending return of Vladimir Putin to the Russian presidency took to the streets of Moscow on Monday, after observers described the previous day's election as tilted in favor of the ex-KGB spy.

Police estimated 14,000 protesters turned out in the city's downtown Pushkin Square chanting, Russia Yes! Putin No! as hundreds of riot-control officers blocked more people from joining the crowd, the Moscow Times reported.

Police arrested dozens of protesters, according to Agence France-Presse, with nearly 100 detained at an unsanctioned post-election rally in St Petersburg.

Among those arrested in Moscow was protest figurehead Alexei Navalny.

They robbed us, Reuters reported Navalny, an anti-corruption blogger, telling the crowd before his detention.

We are the power, he said to chants of Russia without Putin.

Shortly after speaking, black helmeted riot police encircled 35-year-old Navalny and a group of protest leaders before marching them to waiting police vans.

Elsewhere, thousands of Putin supporters, including many from the Nashi youth movement, staged rallies closer to the red walls of the Kremlin, singing songs, waving Russian flags and chanting Prime Minister Putin's name, Reuters reported.

Putin claimed a landslide victory on Monday, taking almost 64 percent of the vote.

A report from international observers with the Organization for Security and Co-Operation in Europe, or OSCE, said the election was riddled with procedural irregularities.

There was no real competition and abuse of government resources ensured that the ultimate winner of the election was never in doubt, Tonino Picula, an OSCE vote monitors was quoted by Reuters as saying.

Conditions [for the campaign] were clearly skewed in favor of ... Vladimir Putin, she said.

The report also alleged that the vote was assessed negatively in almost one-third of polling stations observed due to procedural irregularities.

Putin, who served in Russia's top job from 2000 to 2008, won back the presidency after spending the past four years in the nominally No. 2 role of prime minister.

He will be sworn into office in May and is expected to swap positions with the incumbent president and Putin protege, Dmitry Medvedev.

In France, Foreign Minister Alain Juppe urged Putin to use his victory to steer Russia toward agreement with the international community over Syria.

Russia has totally isolated itself from the rest of the international community in refusing to budge, along with China, from blocking United Nations Security Council resolutions to end violence inflicted by Syrian President Bashar al-Assad's regime against a rebel uprising.