Russia's political opposition Monday claimed a symbolic victory in regional elections while the ruling party said exit polls showed it was headed for a win in a vote observers said was marred by fraud.

The elections were overshadowed by the alleged poisoning of opposition leader Alexei Navalny in the Siberian city of Tomsk ahead of the vote. Germany said Monday that lab tests in France and Sweden confirmed the Kremlin critic was attacked with a Novichok nerve agent.

Russians in dozens of the country's 85 regions voted over several days for governors and lawmakers in regional and city legislatures as well as in several by-elections for national MPs.

The polls came a year ahead of parliamentary elections and were seen as a test for President Vladimir Putin as the ruling United Russia party faces sinking popularity and public anger over economic woes.

In an effort to fight Putin's electoral machine, Navalny urged voters back candidates against the ruling party.

The 44-year-old lawyer and Kremlin critic had been in Siberia to promote a "smart voting" campaign when he was poisoned last month. 

His supporters believe the use of the banned chemical weapon shows that only the Russian state could be responsible. The Kremlin has denounced attempts to blame the Russian state for the poisoning as "absurd".

Two allies of the opposition leader won local parliament seats Monday in the Siberian city of Tomsk where Navalny fell ill, according to early poll results.

United Russia suffered heavy losses in the city of some 500,000, winning just 24.46 percent of the overall vote compared to 52.27 percent in 2015.

Reports of ballot fraud 

Ksenia Fadeyeva, the 28-year-old head of Navalny's Tomsk office who won a city council seat, put her success down to the opposition leader's voting strategy saying "we really campaigned under the Navalny brand".

The result was "a big blow" to United Russia ahead of legislative elections of next year, she told AFP, and also disproved the myth that the opposition only has 2 or 3 percent support.

"But the work continues; no time to rest yet," she said.

In Russia's third-largest city of Novosibirsk, which Navalny also visited during his campaign, his ally Sergei Boyko won a seat on the local council beating out a veteran Communist Party candidate.

United Russia lost 11 seats and their majority on the city council securing 22 places out of 50, with Navalny-backed candidates picking up five spots.

Official results are expected to be announced at the Central Elections Committee Monday.

United Russia chairman Dmitry Medvedev praised Sunday the party's electoral successes, saying that exit polls showed it was heading for victory.

Of 18 regions that voted for governors, 12 elected candidates from United Russia and the remainder chose figures aligned with Kremlin-friendly opposition parties.

The independent election monitor group Golos said it had registered ballot stuffing complaints and received a "stream of reports" that observers were barred from viewing documents and submitting complaints, with conflicts sometimes ending in "fisticuffs".

Chairwoman of the Central Election Commission Ella Pamfilova however said Monday "there were no major violations" and that the vote had seen "fewer flaws than ever," according to the TASS news agency.

Vote organisers said they were holding the ballot between Friday and Sunday to limit the chance of a coronavirus outbreak. But the opposition said the move was a ploy to make it easier for the results to be fabricated.

The European Union denounced the vote held in Crimea, which Russia annexed from Ukraine in 2014, saying it would not recognise "anybody elected in Russia-organised voting in the Crimean peninsula". 

Putin hosted a week-long vote earlier this year on changes to the constitution that make it possible for him to remain in power until 2036, with critics raising concerns over outdoor polling stations and the multi-day vote.