Three Russian opposition activists were on Saturday arrested during an unauthorised gathering of around 100 people in central Moscow, reports said.
The gathering in Pushkin Square was organised as a "meeting", without banners waved or slogans shouted, by far-left activist Sergei Udaltsov of the Left Front movement.
But when two activists tried to unfurl a banner, they were arrested, the Ria Novosti agency said. Another was detained after allegedly attacking pro-Kremlin activists who had come to recite Russian poetry.
The Interfax agency said activists hostile to the opposition supporters had assembled to "pray" near the gathering.
The opposition called for a protest to be held later Saturday close to a square where a large number of police were positioned.
Vladimir Putin, having just served as prime minister, was elected for a third presidential term in a March 4 election with over 63 percent of votes despite months of protests against his regime.