Sergei Udaltsov, a left-leaning opponent of Prime Minister Putin, said demonstrations against Putin's political dominance would culminate in a mass May 5 protest.
"Let's come out to one of Moscow squares and not leave if we're numerous enough," he was quoted by Russia's state-run news agency RIA Novosti as saying. "If the authorities have ignored a rally of a 100,000, we need to bring out more."
Udaltsov was sentenced to 10 days in jail Thursday following his arrest during a weekend demonstration.
Human Rights Watch had said that while the Kremlin was tolerant of dissent during the campaign season, activists were roughed up by authorities after the election.
Putin secured a third non-consecutive term as president in an early March election. The Russian Central Election Commission certified Putin's 46-percentage-point victory over his closet rival, Communist leader Gennady Zyuganov.
Opposition groups had said they wouldn't recognize Putin's victory. He's to be sworn in May 7.
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