* First major elections since Putin returned to Kremlin in May
* Kremlin opponents allege violations including multiple voting
* Five regional leader contests are among nearly 5,000 races
By Gabriela Baczynska and Maria Tsvetkova
KHIMKI/BRYANSK, Russia, Oct 14 (Reuters) - The ruling United Russia party won elections around the country on Sunday, early results showed, but opponents alleged widespread violations in the voting that will preserve President Vladimir Putin's dominance.
The first big elections since Putin began a new six-year term in May will do little to appease opponents who say he has used election fraud and suppression of dissent to maintain his grip on power.
Results from contests from the Baltic Sea to Kamchatka on the Pacific Ocean showed United Russia had won or was heading for victory in all five provincial governorship races, and in several votes for provincial and city legislatures.
Prime Minister Dmitry Medvedev, to whom Putin handed the chairmanship of United Russia after they swapped jobs, said the ruling party had done better than in a December parliamentary election in which it lost dozens of seats.
Charges of fraud in that election brought tens of thousands of people into the streets of Moscow for the biggest opposition protests of Putin's 12-year rule, but he won the presidency in March despite the demonstrations.
"I'll put it frankly: United Russia has made a strong showing, stronger than in the December Duma election," Medvedev said at the United Russia headquarters in Moscow based on results from eastern regions, Russian news agencies reported.
"Everybody expected a party fiasco following the December election... Nothing like that has happened," Medvedev said. He said the elections were "civilised and, as far as I understand, nobody has spotted any significant violations so far."
But opponents accused the Kremlin of using its position to give favoured candidates an unfair advantage by removing competitors from races and pressuring state employees to vote for candidates backed by United Russia.
They also alleged violations in races around the country on election day, including multiple voting and ballot-stuffing.
"It's sad that the situation hasn't changed. The number of violations has not decreased, nor has it increased" compared to previous elections, said Grigory Melkonyants, deputy director of Western-funded vote monitoring group Golos.
"In competitive races violations are conducted without batting an eye. It's nothing new, they continue to conduct ... ballot-stuffing and 'carousels'," he said of a practice in which groups of people cast ballots at several polling stations.
Central Election Commission chief Vladimir Churov said statements by Golos had "nothing to do with reality. We are gathering all the material to further investigate where such a stream of lies is coming from."
The votes included ballots for regional governors in five of Russia's 83 provinces, the first since the Kremlin restored popular elections of regional chiefs, which Putin had scrapped as he tightened control during his 2000-2008 presidency.
The incumbent from United Russia won in the Amur region and partial results showed the party's candidates comfortably ahead in the Novgorod, Belgorod, Ryazan and Bryansk regions, the Central Electoral Commission said.
In Bryansk, in western Russia, a medical worker accused bosses at her clinic of threatening staff with dismissal if they did not vote for incumbent Nikolai Denin at multiple polling stations and record the evidence on their mobile phone cameras.
"I refused, of course," said Maria Makarova, 55, who said she voted for the Communist candidate, Vadim Potomsky.
"What has Denin done in eight years? I get a miserly wage and have to work around the clock to make 6,000 roubles ($190) a month," she said. "He is all talk, and everybody's in poverty."
But Alla, a 72-year-old pensioner who refused to give her last name, said she had voted for Denin. "He did a good thing for my daughter. She has worked in a kindergarten for 25 years and he gave her a good bonus just recently."
A regional election official said the commission had received no formal complaints of pressure on state workers. The governor's spokesman called the claims a "provocation" and said all allegations would be checked.
"There were very many violations" including 'carousel' voting and possibly ballots cast for dead people still on the voter rolls, said a representative of Potomsky's campaign, Yelena Zubtsova.
Among other closely watched votes were the only two contested by prominent leaders of anti-Putin opposition protests: activist and environmental campaigner Yevgeniya Chirikova and liberal politician Vladimir Ryzhkov.
Chirikova cried foul in the Moscow suburb of Khimki, saying hundreds of new residents had been registered in one apartment block alone shortly before the election and accused officials at some polling stations of hiding voter lists from observers.
"New residents were registered early this morning, somehow they received local registration overnight," she said.
With half the ballots counted, United Russia-backed acting mayor Oleg Shakhov led with 46 percent and Chirikova was second with 17 percent, the regional electoral commission said.
The commission chief dismissed Chirikova's claims. Shakhov said she should "learn to lose gracefully."
In the capital of the Altai region, Barnaul, where Ryzhkov was standing, Kremlin opponents said they suspected people were voting at multiple polling stations and that voter rolls had been illegally inflated to boost support for United Russia.
Ryzhkov's party was hovering above the 5 percent threshold needed to win seats in the city legislature, while United Russia was ahead with 50 percent of the votes, according to partial official results.
Churov ordered officials to look into the accusations.
The protests that began in December exposed dismay among many in Moscow and some other cities over Putin's plan to return to the presidency after four years as prime minister, but the protest movement made few inroads deep in the provinces.
In response to the protests, the Kremlin lowered hurdles for registering political parties, meaning more parties were running on Sunday. But opposition groups say many candidates were kept off ballots over minor procedural issues.