Prominent Russian opposition figure Alexei Navalny has registered to stand in September's vote for Moscow mayor.
Police briefly detained Mr Navalny as he addressed supporters outside the city's election commission office where he submitted registration documents.
The anti-corruption blogger, 37, faces a verdict next week in an embezzlement trial.
He denies allegations he took $500,000 from a state timber firm and says the charges are politically motivated.
Mr Navalny faces up to six years in prison if found guilty. He has described the trial as a "political vendetta" planned by the Kremlin to stop his political activity.
The blogger presented documents and 115 signatures necessary for his registration to the Moscow electoral commission before Wednesday's deadline, Interfax news age reports. The commission will decide in the next 10 days whether they are in order, it adds.
The vote was called when Sergei Sobyanin announced he was stepping down before the end of his term. He has also registered for the 8 September election.
Under Russian law, if Mr Navalny is convicted by the court in Kirov - a city 900km (560 miles) north-east of Moscow - he will not be able to run for mayor in Moscow.
He is also understood to harbour presidential ambitions. A guilty verdict could keep him in jail until after the next presidential vote in 2018.
Critics of Russian President Vladimir Putin say Mr Navalny's trial is an example of an increasing clampdown on dissent.