Navalny among hundreds of protesters detained at anti-Putin rallies
Riot police beat protesters with truncheons, dragged them along the ground and threw them into police vans in Moscow, in an attempt to disperse a huge crowd that packed Pushkin Square to protest against President Vladimir Putin's swearing-in ceremony on Monday.
Police grabbed Navalny, 41, soon after he showed up at the rally, as some shouted "Shame" in Ukrainian, a famous slogan of the Kiev uprising that ousted a Kremlin-backed regime in 2014.
Navalny, who was barred from challenging Putin in the March presidential election, had called on Russians to stage a day of rallies across the country under the catchy slogan "Not our Tsar".
Earlier on Saturday, protesters rallied in towns and cities in Russia's Far East and Siberia and some of those protests were violently broken up.
Independent monitoring group OVD-Info said more than 1,000 people had been detained by police nationwide. Of them, more than 470 were detained in Moscow and more than 50 in second city Saint Petersburg.
Police - which put the Moscow turnout at 1,500 people - warned it would use force and "impact munition" against the demonstrators.
Scuffles also broke out between Navalny's supporters and pro-Kremlin activists who descended into the square in an apparent effort to sabotage the opposition demonstration.
Anti-Kremlin protesters chanted "the fourth term - in prison" and "sick of you."
"The country needs changes," said a 20-year-old protester, Stepan Duvanov. "Putin is not a tsar to be sitting (at the Kremlin) forever."
In May 2012, tens of thousands took to the streets to protest Putin's inauguration for a third Kremlin term, with rallies descending into clashes with police.
Criminal charges were brought against around 30 demonstrators and many of them were sentenced to prison terms of between 2.5 years and 4.5 years.
The 65-year-old Putin, who has ruled Russia for almost two decades, was re-elected for a fourth Kremlin term in March.
He recorded his best ever election performance with more than 76 percent of the vote.
Independent monitors said the election was marred by a lack of genuine competition even though fewer irregularities were reported than in previous years.