Russia’s main pro-Kremlin party is claiming a clear win in local polls, seen as a big test of its popularity.
A top United Russia official said all its candidates for governor were well ahead and it was set to win majorities in all regional legislatures.
But the opposition said it won seats in Siberian cities. There have been numerous reports of irregularities.
The polls come only weeks after the suspected poisoning of opposition leader Alexei Navalny with Novichok.
His team had been urging Russians to vote tactically against United Russia.
The Anti-Corruption Foundation had pledged support for candidates it saw as best placed to unseat incumbents of the ruling party, which it describes as the “party of crooks and thieves”.
Mr Navalny’s camp believes this campaign could be why he was attacked, the BBC’s Sarah Rainsford in Moscow says.
His team allege he was poisoned on the orders of President Vladimir Putin – the Kremlin denies any involvement.
Mr Navalny, who fell ill on 20 August in Russia, is now being treated in Germany. Last week, doctors in Berlin’s Charité hospital said he was out of an induced coma and his condition had improved.
Concern about irregularities
Alexey Turchak, the secretary of United Russia’s general council, said the party’s success was based on data from exit polls and preliminary counting.
“All candidates from United Russia in the elections for [governor] are winning convincingly in the first round,” he said, quoted by Russian media.
“Also at the level of legislative assemblies and dumas [parliaments] of the administrative regions United Russia is forming stable majorities in all regions without exception.”
But independent monitoring group Golos has reported that observers have been prevented from viewing documents and making complaints, and that ballot boxes have been stuffed and papers cast by real voters switched.
There were also concerns that early voting allowed on 11-12 September because of the coronavirus outbreak had led to irregularities.
Meanwhile opposition candidates claimed some success.
AFP quoted Kseniya Fadeyeva, the head of Mr Navalny’s office in Tomsk, the city where he was poisoned, as saying she and another Navalny ally had won seats on the city council.
Mr Navalny’s Novosibirsk representative Sergey Boiko also won a council seat in that city.
These are the first elections since controversial constitutional reforms were approved in a July referendum allowing Mr Putin to stay in power until 2036.
They are also seen as a dry run for elections to the national parliament next year.
Last year, mass protests were held in the capital Moscow, following the exclusion of many opposition candidates from a local election.
The authorities were then accused of a heavy-handed response to the rallies, which saw some of more than 1,000 people arrested receive sentences of up to four years in prison.
The far-eastern city of Khabarovsk has seen regular anti-Putin rallies since July, after the arrest of a popular governor fuelled resentment against Moscow’s rule.