The party backing President Putin is heading for a convincing victory in Russia's parliamentary elections.
President Putin faces election himself in March
With more than 90% of the votes counted, the pro-Kremlin United Russia Party leads with almost 37%.
The ultra-nationalist party of Vladimir Zhirinovsky and the Communists are vying for second place.
It seems likely that two liberal, pro-free market parties will fail to get the 5% of votes needed to win party list seats in the State Duma.
Experts say Mr Putin now seems assured of gaining a second term in presidential elections next March.
If United Russia and its allies gain a two-thirds majority, they would be able to amend the Russian constitution, potentially paving the way for Mr Putin to stand for a third term as president.
Exit polls suggest he will control around 60% of the lower house of parliament - just short of this - but some analysts believe the Kremlin could make deals with some independent deputies to achieve its aim.
Twenty-three parties are competing for half of the 450 places in the State Duma of parliament in the fourth such election since the collapse of communism.
The other 225 seats are being contested by individual candidates on a first-past-the-post basis.
Foreign observers and other parties said that the campaign was marred by open bias in favour of United Russia in the media.
The turnout was put at over 30% - well above the 25% mark needed to validate the poll.
The election will decide the make-up of the Duma for the next four years.
The BBC's Stephen Dalziel says the slight polarisation in voting for the two second place parties does not necessarily spell trouble for Mr Putin.
The misleadingly named Liberal Democrats will be expected to support the president on most of his decisions as they did in his last parliament, he says.
PARTIAL RESULTS (90.58% OF VOTES COUNTED)
United Russia (Yedinaya Rossiya) 36.8%
Communist Party 12.7%
Liberal Democratic Party 11.8%
Motherland (Rodina) 9%
Union of Right Forces (SPS) 3.9%
Agrarian Party 3.8%
Source: Election Commission
But the result is being seen as a major defeat for the Communists, who have been a dominant force in the Duma for the past decade and were considered the greatest threat to the Kremlin.
Liberal parties opposed to Mr Putin have also fared badly.
Both the Union of Right Forces and Yabloko currently have around 4% and may not be able to rely on stronger support in Moscow and St Petersburg - which have not yet finished counting - to push them over the 5% threshold.
Mr Putin is also likely to be boosted by the success of the Motherland Party, which is expected to come fourth with around 9% despite being set up only a few months ago.
Analysts say Motherland was created by Kremlin insiders with the aim of taking away votes from the Communists.
Mr Putin, whose popularity ratings top 80%, cast his ballot
with his wife, Lyudmila, at an institute in southern Moscow.
Central Election chief Alexander Veshnyakov has promised to publish results from across the country's 11 time zones on the internet within 24 hours of polling stations closing.
Lyubov Sliska, a senior figure in United Russia, said the result meant democratic reforms would continue.
"This is a serious victory we can rightly be proud of," she said.
But Communist leader Gennady Zyuganov denounced the elections as a "shameful farce".
"You are all participants here in a revolting spectacle which for some reason is called an election," he said after exit polls were published.
"We are living in an authoritarian regime," said Yabloko leader Grigory Yavlinsky, adding that the presidential administration had used all its resources to bring about United Russia's victory.
Our correspondent says that if Mr Putin has a Duma which largely supports him, it will be more difficult for any challenger in the presidential elections next March.
After nearly four years in the Kremlin, Mr Putin, the former head of the secret police, still appears to be riding a wave of genuine support.
The hard line his administration has taken against corruption and wealthy oligarchs has gone down well with voters.
More than 1,100 international observers from 48 states have been accredited for the election, but their numbers may increase to 2,000.