Updated Aug. 10, 2019, 12:15p.m.
Tens of thousands of people converged on central Moscow Saturday to protest the exclusion of several opposition candidates from the upcoming city council election.
The Moscow protest, one of Russia's largest since President Vladimir Putin was re-elected in 2012, was among several in the country.
The White Counter, a non-governmental organization that tracks protest participants, said nearly 50,000 were participating in the Moscow rally, much higher than the Moscow police figure of 20,000.
The protest monitoring group OVD-Info reported scores of arrests in Moscow and at other opposition demonstrations in St. Petersburg and Roston-on-Don.
Lyubov Sobol, who is one of the opposition candidates, was detained at her Moscow office as she was updating supporters on social media before the sanctioned Moscow protest began.
A video on Sobol's Twitter feed shows police in riot gear breaking into her office and demanding that journalists who were present to stand against the wall and put away their cell phones.
Russian opposition candidate and lawyer at the Foundation for Fighting Corruption Lyubov Sobol, center, and others stand in front of a police line during a protest in Moscow, Russia, July 14, 2019.
Sobol, an ally of Kremlin critic Alexei Navalny, chronicled the event as it unfolded. "Look, they are breaking the door right now," she said. "They will enter right now. I am not afraid. I will not give up. I am asking to get my lawyer and will continue my political activities."
Her arrest came as a protest was about to begin for the third consecutive weekend on the issue. Thousands of people were arrested in the two previous protests that occasionally turned violent.
Some opposition activists have called for an unauthorized march in central Moscow after Saturday's authorized rally, prompting a warning from Moscow police and the powerful Investigative Committee that unsanctioned protests would be "immediately halted."
The protesters are calling for free and fair elections in the Moscow city council race next month.
Since being founded in 2011, Navalny’s FBK corruption monitoring organization has published reports detailing the lavish lifestyles of figures close to Russian President Vladimir Putin, including Prime Minister Dmitry Medvedev and Moscow first deputy mayor Natalia Sergunina.