The Kremlin has rejected concerns about Sunday's parliamentary election which gave President Vladimir Putin's United Russia party an overwhelming victory.
More than 60% of the voters cast their ballots, officials say
Mr Putin called his party's two-thirds share of the vote a sign of political stability and thanked the electorate for turning out in high numbers.
International observers and some western governments have expressed concern about the poll's conduct.
The German government said Russia was not a democracy.
BBC Moscow correspondent James Rodgers says the main question now is what Mr Putin will do with his big majority.
With nearly all ballots counted, Mr Putin's United Russia had 64.1% of the vote, the electoral commission said. Turnout was about 63%.
The Communist Party, with 11.6% of the vote, was the only opposition party to gain seats in the State Duma, while liberal opposition parties looked certain to fall below the 7% threshold needed to enter parliament.
Two parties allied to the Kremlin - A Fair Russia and the right-wing Liberal Democratic Party - were also poised to win seats.
Kremlin spokesman Dmitry Peskov told the BBC the election had been free and fair and that any allegations of voting irregularities would be investigated.
"In general what we saw yesterday is just and fair democratic elections," he said.
Mr Putin described the election as a "good example of domestic political stability".
Foreign observers from the Organisation for Security and Co-operation in Europe and the Council of Europe said the election was "not fair".
It "failed to meet many OSCE and Council of Europe commitments and standards for democratic elections", they said.
The independent Russian monitoring group, Golos, reported various violations during the voting, which it said amounted to "an organised campaign".
In some cases, it said, state employees and students were pressured to vote, and those voting for United Russia were entered into a prize lottery in St Petersburg.
The German government said the elections were neither free nor fair and it called for Russia to embrace multi-party politics.
The White House said it urged the Russian authorities to investigate alleged violations.
Mr Putin is constitutionally obliged to stand down after his second term as president ends in March next year.
Mr Putin's next steps will be keenly watched at home and abroad
The BBC's James Rodgers in Moscow says his party's win will enable him to continue wielding great influence in politics - even if he is no longer in high office.
Mr Putin announced this year he may seek the office of prime minister after his presidential term ends.
Even Kremlin insiders admit to being in the dark about what their boss is thinking, our correspondent says.
President Putin could become prime minister or take up another post while his opponents suspect he may use this new mandate to change the law and stay in office, he adds.