Russian opposition activist, Alexei Navalny, has refused to concede defeat in Moscow's mayoral elections, demanding a runoff after official results showed pro-Kremlin incumbent Sergei Sobyanin was set to win in the first round.

"What we are seeing now are clear falsifications," Navalny, 37, told reporters in a late Sunday night briefing at his campaign headquarters in the capital, Moscow.

Initial results showed that Sobyanin, a leading ally of President Vladimir Putin, would narrowly win in the first round with just over half the vote after Navalny picked up over a quarter of the ballots.

Sobyanin was winning 51.4 percent of the vote with Navalny on 27.2 percent, the Moscow election commission said in a count based on over 80 percent of polling stations reporting.

Navalny, who is a major critic of President Putin, insisted he had managed to force the mayor into a second round and threatened street protests if the authorities did not acknowledge Sobyanin had polled less than 50 percent.

"We demand that a second round is held. If that is not done... we will appeal to the citizens and ask them to take to the streets of Moscow."

In a nationwide day of local polls that may worry the Kremlin, opposition anti-drugs campaigner Yevgeny Roizman defeated the pro-Kremlin candidate in elections for Russia's fourth largest city Yekaterinburg.

In a late-night rally in central Moscow attended by thousands and lit up by fireworks, Sobyanin had said he was sure of victory and congratulated himself for organising "the most honest and open elections in the history of Moscow".

"We have something to be proud of," he told the cheering supporters.

But turnout was low at 26.5 percent as of 1400 GMT, an unusually slack figure, which indicated Navalny had been far more successful at bringing out his supporters than the mayor, who ran a supremely low-key campaign.

Communist candidate Ivan Melnikov was third in the partial results with just over 10.6 percent of the vote, while other contenders merely made up the numbers. Muscovites had six candidates to choose from.

The candidacy of Navalny - who campaigned under the shadow of a conviction in a controversial embezzlement case - made the race the first genuinely competitive Russian election since the heady early post-Soviet years.

Putin support

The election was seen as a crucial test of the protest mood in the city, which was shaken by huge demonstrations against Putin's decade-long rule in the winter of 2011-2012.

"This is a victory for Navalny, the results he's received are very good, even if there will be no run-off," Gleb Pavlovsky, a political analyst and one-time Kremlin consultant, told AFP news agency.

Putin, who made no secret of his support for his former Kremlin chief of staff Sobyanin, said Moscow did not need a politician for a mayor.

"Such big cities do not so much need to be run by politicians," he said after casting his vote in Moscow, adding such a city should be managed by "depoliticised people, technocrats".

Al Jazeera’s Peter Sharp, reporting from Moscow, said Navalny had been carrying out the “first-ever Western-style political campaign, using social media and political slogans such as 'change Russia, start with Moscow'".

In July, Navalny was sentenced to five years in a penal colony on fraud charges that he says were trumped up and arrested in court.

A day later he was suddenly released pending his appeal, in an unprecedented move observers say showed the Kremlin did not know how to handle him. 

Sobyanin, appointed to a five-year term by the Kremlin in 2010, had called an early election to bolster legitimacy and strengthen his position.

Source: Al Jazeera and agencies