Russian opposition leader Alexei Navalny and more than 1,600 anti-Kremlin activists have been detained by police during street protests against Vladimir Putin ahead of his inauguration for a fourth presidential term.
Mr Navalny had called for people to take to the streets in more than 90 towns and cities across the world's largest country to register their opposition to what Mr Navalny says is Mr Putin's autocratic Tsar-like rule.
Mr Putin won a landslide re-election victory in March, extending his grip over Russia for six more years until 2024, making him the longest-lasting leader since Soviet dictator Josef Stalin, who ruled for nearly 30 years.
Mr Navalny, who was barred from running in the election against Putin on what he says was a false pretext, was detained soon after showing up on Moscow's central Pushkinskaya Square where young people chanted "Russia without Putin" and "Down with the Tsar".
Footage of the detention posted online showed five policemen carting him off to a waiting van by his arms and legs.
Mr Navalny, who has been detained and jailed for organising similar protests in the past, had managed to briefly address several thousand people beforehand, saying he was glad people had shown up.
Reporters saw riot police systematically detaining other protesters in Moscow, some of them harshly, before bundling them into buses.
In St Petersburg, protesters were prevented from reaching the city's central square.
Pavel Kuznetsov, a 72-year-old pensioner wearing a t-shirt depicting Mr Putin wearing a crown with a line through it, said he and others had turned up in Moscow to protest against what he said was an election designed to keep a dictator in power.
"We've come out here to demonstrate against the puppet elections," he said.
OVD Info, a human rights organisation that monitors detentions, said it had received reports of police detaining 1,607 people across the country, 704 in Moscow alone.
While police said protesters in the capital numbered around 1,500, eyewitnesses estimated the crowd exceeded several thousand.
Protests took place in the Far East and Siberia as well.
In the Urals city of Yekaterinburg, around 1,500 kilometres east of Moscow, a reporter saw a crowd of more than 1,000 people protesting, some shouting "Down with the Tsar".
Mr Putin, 65, has been in power, either as president or prime minister, since 2000.
Backed by state TV and the ruling party, and credited with an approval rating of around 80 percent, he is lauded by supporters as a father-of-the-nation figure who has restored national pride and expanded Moscow's global clout with interventions in Syria and Ukraine.
The authorities regard most of the protests as illegal, arguing their time and place was not agreed with them beforehand.
Mr Putin dismissed Mr Navalny as a troublemaker bent on sowing chaos on behalf of Washington.
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Prime Minister Dmitry Medvedev, a close Putin ally, has called Mr Navalny a political charlatan.
Mr Putin is due to be inaugurated on Monday in a Kremlin ceremony heavy on pomp and circumstance.
With almost 77 percent of the vote and more than 56 million votes, his March election win was his biggest ever and the largest by any post-Soviet Russian leader, something he and his allies say gave him an unequivocal mandate to govern.
However, European observers said there had been no real choice in the election, and complained of unfair pressure on critical voices.
Critics like Mr Navalny accuse Mr Putin of overseeing a corrupt authoritarian system and of illegally annexing Ukraine's Crimea in 2014, a move that isolated Russia internationally.