Protests against Vladimir Putin ahead of his inauguration for a fourth presidential term have taken place across Russia.
Critics say Mr Putin is more of a tsar than a democratic leader.
Russian opposition leader Alexei Navalny was detained at a rally in central Moscow, while dozens of his supporters were arrested during nationwide protests.
Mr Putin, 65, was re-elected in a landslide victory in March - extending his grip over the world's largest country until 2024. He will be inaugurated on Monday.
He has been in power, either as president or prime minister, since 2000.
His victory makes him the longest-lasting leader since Soviet dictator Joseph Stalin, who ruled for nearly 30 years.
— Kevin Rothrock (@KevinRothrock) May 5, 2018
Mr Navalny, who has been repeatedly detained and jailed for organising protests, published a message ahead of the marches saying: "If you think that he is not our tsar, take to the streets of your cities.
"We will force the authorities, made up of swindlers and thieves, to reckon with the millions of citizens who did not vote for Putin."
Mr Navalny called for rallies in more than 90 towns and cities, including Moscow and St Petersburg.
A Twitter account supporting Mr Navalny posted images from the protests, showing a stream of people waving Russian flags and carrying red balloons.
Russian police detain a protester at a demonstration against President Vladimir Putin in Pushkin Square in Moscow, 05-05-2018. Image: AP/Press Association Images
The authorities regard most of the protests as illegal, arguing that their time and place was not agreed with them beforehand.
Police have broken up similar demonstrations in the past, sometimes harshly, detaining hundreds.
One activist told a crowd in the city of Khabarovsk: "Putin has already been on his throne for 18 years! We've ended up in a dead end over these 18 years. I don't want to put up with this!"
A fighter of National Liberation Movement pushes a protester down, during clashes at a demonstration against President Vladimir Putin in Pushkin Square in Moscow, 05-05-2018. Image: AP/Press Association Images
Mr Putin boasts an approval rating of around 80%. He is backed by state TV and the ruling party.
Supporters see him as a father-of-the-nation figure who has restored national pride and expanded Moscow’s global power.
Mr Putin has dismissed Mr Navalny, who was barred from running in the presidential election on what he said was a trumped-up pretext, as a troublemaker bent on sowing chaos on behalf of Washington.