United Russia secured 57.9 per cent of the vote after more than 50 per cent of ballots had been counted, Interfax reported, citing the election commission.
The vote has been dismissed by democracy watchdogs, foreign governments and Kremlin opponents as neither free nor fair, with critics accusing authorities of excluding genuine opposition and tightly controlling the political landscape.
The anti-war Yabloko party was barred from the election while all parties represented in the outgoing parliament are considered loyal to the Kremlin and support Russia's war against Ukraine.
According to preliminary estimates, the United Russia party was set to win 309 of the 450 seats in the State Duma, including direct mandates, nine more seats than are needed to amend the constitution, Novaya Gazeta reported.
The election was Russia's first parliamentary vote since President Vladimir Putin launched the full-scale invasion of Ukraine in February 2022 and was widely seen as a test of public backing for the war.
The Communist Party won 13.8 per cent of the vote, followed by the ultranationalist LDPR on 8.8 per cent and New People on 7.9 per cent, according to the initial results.
A Just Russia was on 5.1 per cent, putting all four parties on course to return to the State Duma.
Official figures put turnout at more than 56 per cent, higher than in the 2021 parliamentary election. Figures provided by Russia's electoral authorities cannot be independently verified.
Despite Ukraine's protests, the election was held for the first time in the Russian-controlled parts of the annexed Ukrainian regions of Luhansk, Donetsk, Zaporizhzhya and Kherson. The Black Sea peninsula of Crimea, which was annexed back in 2014, was once again included.
Yabloko, which was initially approved to stand before being removed from the ballot, and the traditionally strong Communist Party both complained that hundreds of their observers had been prevented from monitoring polling stations.
Civil servants also reported being pressured to vote, while there were allegations of ballot stuffing, as in previous Russian elections.
Some voters complained that they had not received polling cards and had been registered for online voting without their knowledge.
Electronic voting in Russia has faced criticism over a lack of transparency and concerns about possible manipulation.
with AP and Reuters
19°C