Violent clashes broke out across Russia Sunday, as police detained over 5,000 protesters demanding the release of jailed government critic Alexei Navalny.
In St. Petersburg, police were seen using batons to beat protesters, and electric tasers.
In the heart of Russia's capital, Moscow, police imposed a sweeping security lockdown in a massive show of force, sealing off streets and walkways near the Kremlin, closing metro stations, and deploying hundreds of riot police.
Chanting "Putin is a killer" and "Navalny is a hero," protesters braved negative degree temperatures and snowfall, while they marched toward the prison where Navalny is detained in northern Moscow.
Massive rallies have swept Russia since Navalny, President Vladimir Putin's most prominent opponent, called on his supporters to protest after he was arrested on January 17.
That was shortly after Navalny returned to Russia for the first time since being poisoned with a nerve agent there last summer.
He has accused Putin of ordering his murder, which the Kremlin denies.
U.S. Secretary of State Antony Blinken and UK Foreign Minister Dominic Raab are among those who have called for Navalny's release.
Many of Navalny's most prominent allies were also targeted in this past week's crackdown.
His wife, Yulia Navalnaya, was among those detained, though she was later released.
Several, including his brother Oleg, are still under house arrest.