Moscow: Russians voted on Sunday in Presidential polls set to return strongman Vladimir Putin to the Kremlin for an unprecedented third term, as he faced public wrath over allegations of rigging in December's parliamentary elections which was won by his United Russia party.

Voters turned out at 90,000 polling stations across Russia spread over 21 hours for the marathon electoral process, that is being monitored through election observers and over 100,000 webcams.

Sunday’s vote sees Putin, the 59-year-old ex-KGB spy hoping to become president for a third time after swapping role as Prime Minister with his close aide Dmitry Medvedev.

Putin voted in Moscow with his wife, Ludmila. "I'm expecting a good turnout, because presidential elections are an important event. I am confident that people will act responsibly", he told Russian media.

Putin's main challenger is considered to be Communist Gennady Zyuganov, who is running for a fourth time. If Putin fails to achieve more than 50 percent of the vote he will face his nearest rival in a run-off.

The other candidates are ultra-nationalist Vladimir Zhirinovsky, tycoon Mikhail Prokhorov, who is standing as an independent, and former upper house speaker Sergey Mironov, from the centre-left A Just Russia party.

Putin was Russia's president from 2000 to 2008, but was barred by the constitution from standing for a third consecutive term. He faces four challengers, three of whom he has defeated in previous elections.

The election is being held against a backdrop of popular discontent, sparked by allegations of widespread fraud during December's parliamentary elections in favour of Putin's United Russia party. Experts say there is real debate as to whether Putin remains the best person to lead Russia, or whether the time has come for change.

"We have been visiting here in Novosibirsk, just over 41 percent of registered voters had cast their ballots by 2pm local time - the half-way point in voting day," a top election official said.

As in the rest of the country, webcams are up and running in the polling station. Around the room which houses the large, transparent ballot boxes, observers are sitting, quietly keeping an eye on the voting process.

Novosibirsk, like many cities, has seen an upsurge in people volunteering to monitor the election.

Activists, angered by the evidence of rigging in last December's parliamentary election, organised a training programme which created thousands of new monitors.

The conclusions they and other Russian and international monitoring teams reach on whether this election was free and fair will be critical for the legitimacy of the country's new President.

The Interior Ministry is bringing 6,000 police reinforcements to Moscow from the regions, according to Russian media reports.

However, the liberal opposition behind some of the recent protests is not represented. The so-called white-ribbon movement has attracted more than 50,000 people in recent demonstrations in Moscow and other major cities, after widespread allegations of vote-rigging during elections for the State Duma. Similar numbers attended pro-Putin and pro-Communist rallies.

Putin has responded by announcing a programme to install webcams in each of the country's polling stations, but critics have questioned their effectiveness. A joint mission by the OSCE and the Parliamentary Assembly of the Council of Europe comprising 250 observers is monitoring the elections.

Meanwhile tens of thousands of Russians have volunteered as election observers and been trained to recognise and report violations.

(Agencies)