Russian opposition leader held

Navalny was detained immediately after leaving the stage of a campaign event. Ten technicians who were working to dismantle the stage were also arrested, according to members of the Navalny campaign.

One of Putin's biggest critics and an anti-corruption blogger, Navalny was led to a waiting police van and taken away after addressing several thousand people outside a Moscow park on Sunday.

Police said he was questioned about holding an unsanctioned meeting that "violated the rights and legal interests" of others. But he was quickly released and confirmed via his Twitter account that he had been freed and added: "All is well."

One aide at the rally said authorities were putting pressure on Navalny in an attempt to disrupt his campaign to oust Moscow's pro-Kremlin mayor, Sergei Sobyanin.

Opinion polls show Navalny has little chance of defeating Sobyanin and indicate that Putin remains popular with voters.

A Moscow court last week rejected Navalny's attempt to have Sobyanin disqualified on a technicality. An electoral official said Navalny himself might be thrown out for violating rules on the funding of campaign materials.

Navalny, 37, has appealed a five-year prison sentence after being found guilty last month of stealing timber from a state firm. He says the charges were invented as Putin's revenge for the protests.

jm/lw (Reuters, AP)