Russian police on Sunday briefly detained top Kremlin critic Alexei Navalny after a campaign rally for the Moscow mayoral election he is contesting next month, police said.
Violations of the law on mass protests were at issue, the police said in a statement about half an hour after taking the opposition leader away in a van following a rally for the September 8 vote.
"Free", his spokeswoman Anna Veduta tweeted after the sight of Navalny being driven away in a police van sparked fears that the opposition leader could return to jail a month after his release.
"One of the candidates for Moscow mayor was Sunday invited to the police station for a chat on violations of the law on mass demonstrations," a police spokesman told the Interfax news agency.
"The citizen left the police station after this chat," the spokesman said.
"Everything's fine," Navalny himself tweeted moments later. "The police chief offered me an apple ('from his dacha') and said I was totally free."
Veduta had previously said on Twitter that the rally in a northeastern neighbourhood of the Russian capital was attended by 5,000 to 7,000 people.
According to AFP reporters, young men in civilian clothes attempted to disrupt the rally by clipping electric cables hooked up to the stage.
Navalny, an eloquent lawyer who fearlessly mocks President Vladimir Putin, has been holding daily rallies, speaking in televised debates and peppering the city with posters, despite facing a five-year jail term.
Last month he was convicted of embezzlement in a disputed verdict, but in a surprise move a court postponed his sentence to allow him to run as mayor.
An opinion poll released this month showed Navalny a distant second in the mayoral race, with 13 percent of the vote to 67 percent for Kremlin favourite Sergei Sobyanin.
However another survey gave Navalny, who has vowed to force a runoff, close to 20 percent.
Moscow election commission chief Valentin Gorbunov said Thursday the panel would consider disqualifying Navalny "if the violations exceed the norms established by the law."