Russian opposition leader Alexei Navalny and hundreds of anti-Kremlin activists were arrested by police amid protests against Russian President Vladimir Putin in Moscow on Saturday.

The Associated Press reports that Navalny, an anti-corruption campaigner, was one of the organizers of demonstrations that led thousands across Russia to protest the upcoming inauguration of Putin to a fourth term as president.

In Moscow, thousands of demonstrators gathered at Pushkin Square. Police in riot gear joined the crowd at the square and arrested Navalny, the AP reported.

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Navalny was reportedly seen struggling as police carried him out of the square by his legs and arms.

OVD-Info, an organization that monitors arrests during mass protests, said it received reports of more than 1,000 people across Russia being detained by police, with nearly 500 in Moscow alone, Reuters reported.

The demonstrations come as Putin is scheduled to be inaugurated on Monday for another six-year term. Putin’s election, in which he won 77 percent of the vote, has been criticized for a number of voting irregularities. President Trump congratulated Putin on his win earlier this year.

Navalny attempted to run for president in the 2018 election but was barred by Russia's Central Election Commission. He was arrested in January after organizing a protest urging Russians to boycott the March presidential election.

Updated: 10:55 a.m.