United Russia had registered slight losses compared to the last election in 2016, Election Commissioner Ella Pamfilova said.

With almost all ballots counted, United Russia received 49.6 per cent of votes, down from 54.2 per cent five years ago.

According to Pamfilova, five parties will be represented in the country's lower house, the State Duma.

Besides United Russia, those are the communists, the Liberal Democratic Party of Russia (LDPR) of ultra-nationalist Vladimir Zhirinovsky, the A Just Russia party and the New People party which cracked the five-per-cent hurdle for the first time.

Observers and members of the opposition in Moscow on Monday demanded the city's online voting results in Russia's parliamentary elections be declared void.

"We do not recognise the results of electronic voting in Moscow," Russian Communist Party deputy leader Dmitry Novikov said.

Moscow's online results were only published on Monday afternoon while in other regions they were already available hours after polls closed on Sunday evening.

The independent voter rights organisation Golos spoke of clearly verifiable fraud and called on the election commission to annul the results.

Golos' Roman Udot said on Facebook that 78,000 more ballot papers were shown for online voting than were given to eligible voters.

In most of Moscow's constituencies, candidates from parties other than United Russia were in the lead following the count of ballots at polling stations but they were suddenly overtaken by United Russia candidates when the results of the online vote came in.

Australian Associated Press