Russian opposition leader Aleksei Navalny, a candidate in next month's election for Moscow mayor, has been detained briefly after a campaign rally.
Navalny, a fierce critic of Russian President Vladimir Putin and an anticorruption campaigner and blogger, was detained onAugust 25 after a rally in the Sokolniki neighborhood of Moscow.
RFE/RL's Russian Service reported that the rally was attended by at least 5,000 people.
Video footage showed Navalny being escorted from the rally and taken away in a police bus.
A police spokesman said Navalny was "invited" to a police station to give explanations "in connection with offenses against legislation on mass events," but was later released.
The spokesman did not elaborate on the alleged offenses.
But media reports said young men in civilian clothes attempted to disrupt the rally by clipping electric cables hooked up to the stage.
On August 22, Moscow city Election Commission chief Valentin Gorbunov said officials were looking into alleged campaign violations by Navalny that could disqualify him from running in the September 8 poll.
Navalny was sentenced to five years in prison on July 18 after being found guilty of defrauding a lumber firm of $500,000 when he was an adviser to the Kirov governor in 2009.
Navalny was later released pending an appeal.
Navalny has rejected his conviction -- which was heavily criticized by Western countries -- as politically motivated.
Navalny has been campaigning actively, holding daily rallies and speaking in televised debates.
An opinion poll released this month showed the opposition leader a distant second in the mayoral race, with 13 percent of the vote to 67 percent for incumbent and Kremlin favorite Sergei Sobyanin.
However, another survey gave Navalny close to 20 percent.
A runoff would take place between the top two candidates if no one wins more than 50 percent of the vote.
With reporting by AFP, Interfax, Lenta.ru, and RFE/RL's Russian Service