United Russia, backed by President Vladimir Putin, has won a majority in the country’s parliamentary election, far ahead of rival parties.
With 93% of the votes counted, the party has secured 54.2% of ballots and 343 seats in the 450-member parliament, officials say.
Mr Putin said his party had “achieved a very good result”, however the turnout was a record low 47%.
The Communist party and nationalist LDPR both secured just over 13%.
A Just Russia party gained just over 6% of the votes. All four parties had dominated the last parliament, or State Duma.
Voting irregularities were reported in several areas and the head of the election commission suggested that the results might be cancelled in three polling stations.
Liberal opposition parties failed to get enough votes for party-list representation. “To my utmost regret, not one other party managed to get over the 5% barrier,” said Central Election Commission head Ella Pamfilova.
The two main opposition parties allowed to field candidates, Yabloko and Parnas, received just 1.89% and 0.7% respectively.
Half the seats were also being contested in constituencies but even there the small number of opposition candidates failed to win.
The result increases United Russia’s majority after it achieved 49% of the vote in the 2011 Duma elections. The party, led by Prime Minister Dmitry Medvedev, will also take more seats in parliament, up from 238.
However, the turnout, based on partial figures, was the lowest in Russia’s modern history and significantly down on the 60% turnout in 2011.
The head of the election commission had said earlier that she was “fully confident that the elections are proceeding in a quite legitimate way”, but she later warned that results at three polling stations might be cancelled because of irregularities.
Elsewhere there were reports of serious irregularities in one Siberian region, with suggestions of “carousel” voting – people bussed around polling stations – in the city of Barnaul.
Monitoring group Golos said it had received more than 1,300 complaints from around the country by late afternoon, AP reports.
For the first time, people voted in Crimea, annexed from Ukraine in 2014 in a move condemned internationally. United Russia won all the region’s constituency seats in a vote that prompted protests in the Ukrainian capital, Kiev.
In the system of “Managed Democracy” crafted by the Kremlin, it was unthinkable that President Putin’s control of parliament would weaken.
And so, the four pro-Kremlin parties which dominated the previous parliament will do so again. But will the new parliament be recognised by the public as legitimate?
The Russian authorities have tried to present this as one of the cleanest elections in years. Some opposition candidates were permitted to run; a respected human rights advocate was appointed head of the Russian Election Commission.
Yet throughout the day there have been reports of voting fraud – and video to back them up. In some cases, webcams installed at polling stations recorded what appear to be election officials stuffing ballot boxes.
It was vote-rigging which sparked anti-government street protests after the last parliamentary election. President Putin will be hoping that this time his personal popularity, combined with widespread apathy, will mean that Russians accept the result.
Allegations of fraud after the 2011 election sparked large-scale protests against Mr Putin in Moscow and the authorities were anxious to oversee trouble-free polls this time.
Mr Putin has enjoyed 17 years in power as either president or prime minister.
After the vote he visited the headquarters of United Russia with Mr Medvedev to congratulate activists on their victory.
“We know that life is hard for people, there are lots of problems, lots of unresolved problems,” Mr Putin said. “Nevertheless, we have this result.”
Despite Russia’s economic malaise and tensions with the West over the conflicts in Ukraine and Syria, the poor turnout reflected widespread apathy among voters. Some observers had called the election campaign the dullest in recent memory.