MOSCOW (Reuters) - Vladimir Putin's ruling party suffered a big drop in support in a parliamentary election on Sunday, exit polls showed, as voters signalled their growing unease with his domination of Russian politics before a planned return to the presidency next year.
Two exit polls suggested Putin's party, United Russia, would win 45.5 and or 48.5 percent of the votes in the election to the State Duma compared with 64.3 percent in 2007 and that it could struggle even to hold on to a majority in the chamber.
The vote was widely seen as a test of Putin's personal authority after signs that Russians have started to tire of his tough-guy image, built up by his crushing of a rebellion in revel Chehnya and antics such as bare-chested horse riding.
"Russia has a new political reality even if they rewrite everything," said Sergei Obukhov, a parliamentary deputy of the Communist Party, which made considerable gains, its vote almost doubling to around 20 percent, according to the exit poll.
A United Russia leader, Boris Gryzlov, looked stunned when he addressed reporters after voting ended but claimed victory and said: "We are watching and hope that we shall get a majority of the mandate in the State Duma".
"We can say that United Russia remains the ruling party."
But there can be little to cheer Putin, who has dominated Russian politics since becoming president in 2000 and serving in the post until 2008. In that year he was obliged to step down, the constitution preventing him serving more than two consecutive terms.
Official results after about 10 percent of the votes had been counted showed United Russia with 45.9 percent of the vote and the communists with 20.7 percent.
The exit poll did not make clear how the 450 seats in the Duma would be shared out under complicated calculations. But one poll projected United Russia, which has dominated the chamber since 2003, would have only 220 seats.
The communist party emerged in second place in both polls with considerable gains over 2007.
Putin remains by far the most popular politician in the vast country of more than 140 million people but there have been signs that some Russians are wearying of his cultivated strong-man image after 12 years in power.
"United Russia has lost touch with reality," said a 30-year-old history teacher in St Petersburg who gave his name only as Alexander.
Putin is still almost certain to win the March 4 presidential election and could extend his rule until 2024 if he wins the maximum two more terms.
The 59-year-old ex-spy looked stern and said only that he hoped for good results for his ruling United Russia party as he walked past supporters to vote in Moscow.
The result was also a blow for President Dmitry Medvedev, who is standing down to allow Putin to resume the presidency he ceded to him in 2008. Medvedev, who would take over the prime minister's office from Putin next year, had led the election campaign.
His position could now be in question.
Opposition parties complained of election irregularities in parts of the country spanning 9,000 km (5,600 miles) and a Western-financed electoral watchdog and two liberal media outlets said their sites had been shut down by hackers intent on silencing allegations of violations.
Sites belonging to the Ekho Moskvy radio station, online news portal Slon.ru and the watchdog Golos went down at around 8 a.m.
"Massive cyber attacks are taking place on the sites of Golos and the map showing violations," Golos said on Twitter.
Medvedev has dismissed talk of electoral fraud.
Supporters say Putin saved Russia during his 2000-2008 presidency, restoring Kremlin control over sprawling regions and reviving an economy mired in post-Soviet chaos.
His use of military force to crush a rebellion in the southern Muslim region of Chechnya also won him broad support, and security was tight there on election day.
Opposition parties say the election was unfair from the start because of authorities' support for United Russia with cash and television air time.
Putin has no serious personal rivals as Russia's leader. He remains the ultimate arbiter between the clans which control the world's biggest energy producer.
But his party has had to fight against opponents who have branded it a collection of "swindlers and thieves" and combat a growing sense of unease among voters at Putin's grip on power.
Sports fans booed and whistled at Putin at a Moscow martial arts fight last month -- an exceptional event in a country inclined to show respect and restraint towards leaders.
Writing by Timothy Heritage, Editing by Ralph Boulton