Russian President Vladimir Putin's top critic Alexei Navalny was set on Friday to hold the final rally of his fierce campaign for Moscow mayor before facing a Kremlin-backed incumbent in polls this weekend.

Defying gloomy weather and cold drizzle, the 37-year-old blogger was planning to rally his supporters at Moscow's centrally located Sakharova Avenue, where he first roused huge crowds during unprecedented protests against Putin's 13-year rule in winter 2011.

Prominent rockers were set to sing late in the afternoon in support of the main opposition candidate, who has campaigned under the burden of a five-year sentence on fraud charges that he condemns as politically motivated.

Kremlin-backed incumbent Sergei Sobyanin will hold a rival rally at a hulking Soviet-era sports complex, while four other candidates were also scheduled to meet their supporters.

Muscovites will go to the polls Sunday to elect a mayor for the first time in a decade after the Kremlin first scrapped and then reinstated regional elections following the protests.

Navalny's candidacy has made the race the first genuinely competitive Russian election in years, with many observers seeing the polls as a vote of confidence in Putin's top-down power structure.

According to independent pollster Levada Centre, Sobyanin is set to win the polls with a majority in the first round, while Navalny is expected to come second with 18 percent.

Navalny, who has pledged to jail Putin and his allies if he one day becomes president, insists however that he will force the election into a run-off.

"We will work with an eye towards a second round, and in the second round I will win," he told opposition newspaper Novaya Gazeta in an interview released this week.

With the support of thousands of volunteers, 100 million rubles ($3 million, 2.3 million euros) in donations and countless meetings with everyday Muscovites, Navalny has run what many say is the first Western-style election campaign in Russia.

By contrast, his main rival Sobyanin, 55, has given few interviews and shunned television debates, focusing instead on sprucing up the capital before the vote.

In July, Navalny was sentenced to five years on fraud charges but then suddenly released in court pending appeal, leading some to say he has campaigned not so much for the mayoral post as for his freedom.

If he performs well in the polls, his jail term may be commuted to a suspended sentence, some analysts said.

The opposition leader charges that the authorities are planning to rig the election, and may contest the results by urging his supporters to take to the streets.

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