Russians across 11 time zones voted on Sunday in a Parliamentary election seen as a referendum on President Vladimir Putin's [Images] hold on power even after he quits office in May, with a marginalised opposition crying foul.

In all, 11 parties are in the fray for 450 seats in the State Duma to be allocated on proportional basis, but pollsters suggest United Russia [Images] led by Putin, a former KGB agent who remained at the helm for seven years, will gain a clear majority by bagging over 60 per cent votes.

"Thank God, election campaign is over.... I am in a good, festival-like mood," said a beaming Putin, who had earlier warned his countrymen that Russia would face disintegration if his party is not voted to power, before casting his vote here.

Heavy turnout was reported in the eastern parts of Russia with 109 million registered voters expected to vote in the 95,000 polling booths across the country.

The vote is the first national ballot under new election laws introduced by Putin which have been criticised as a step to marginalise anti-Kremlin parties.

Apart from the seats being awarded proportionately to ballot share, unlike earlier when half of the seats were filled by direct contest, a party must receive at least 7 per cent of the national vote to get any seat- up from 5 per cent.

Gennady Zyuganov, chief of Russian Communist Party, the only potent opposition in the country, termed the ballot the "most complex and undemocratic" and alleged several irregularities.