A senior official of Russia's ruling party has declared it won landslides in local elections across the country, but critics allege ballots were rigged.

The elections to choose the mayor of Moscow and governors of 20 regions were held from Friday through Sunday.

The results published by Russia's Central Election Commission show incumbent Moscow Mayor Sergei Sobyanin, one of President Vladimir Putin's close aides, has won reelection, garnering 76 percent of the votes.

They also show candidates from the ruling United Russia party, which supports the Putin administration, have been elected in most of the regions.

An independent election monitoring group alleges there was rigging in electric balloting and Russian authorities obstructed opposition candidates in the races.

But a senior United Russia official said on social media that the elections were held in a fair manner, and stressed that all the elections concluded with landslide victories for his party.

Former Russian President Dmitry Medvedev, who led the ruling party, said on Sunday that the presidential election is approaching, and his party should begin preparations soon.

He aims to solidify United Russia's power base in the lead-up to the presidential race slated for next March.

Russia is also staging what it calls "elections" in the Donetsk and Luhansk regions in eastern Ukraine, and the Zaporizhzhia and Kherson regions in the south.

Russia unilaterally annexed the four regions last September.

The Central Election Commission has announced that United Russia won 74 to 83 percent of the votes in each of the annexed regions.

European Council President Charles Michel criticized Russia on social media on Monday, saying "the sham continues."

He said, "Russia's attempt to organize fake elections in the illegally occupied areas of Ukraine cannot replace the reality of the brutality of the war." He added that the "EU strongly condemns the illegitimate elections that are a blatant violation of the international law."