Russia's ruling United Russia party said on Monday it had won a two-thirds majority in parliamentary polls that the opposition says were rigged.

United Russia's general council secretary Andrei Turchak told reporters the party would win 120 seats from the party list and 195 single-mandate seats after the three-day election that ended on Sunday, giving it 315 in the 450-member chamber.

Turchak said the party had won a "convincing and clean victory" and had not seen any significant violations during the polls.

He said United Russia had also won in local legislative polls in 39 regions.

The parliamentary and local elections were held following an unprecedented crackdown on the opposition including the imprisonment of top Kremlin critic Alexei Navalny.

With 85 per cent of votes counted, United Russia was ahead with 49.76 per cent of the vote, followed by the Communist Party with 19.61 per cent.

Navalny's allies said the vote was being falsified on a massive scale, pointing especially to repeated delays in releasing the results of electronic voting in liberal and opposition-friendly Moscow.

"This is truly unbelievable. I remember the feeling in 2011, when they stole the election. The same is happening right now," said Navalny's spokeswoman Kira Yarmysh.

Claims of widespread fraud in the 2011 parliamentary elections sparked huge protests led by Navalny.