A protester holds a placard in the colour of the Ukrainian flag during a rally against Russia's military operation in Ukraine during a rally in Rennes, western France on February 24, 2022.

Russia's invasion of Ukraine has sparked fierce, widespread outrage and condemnation around the world from global leaders, military experts and grassroots protesters alike.

Russian President Vladimir Putin's military aggression — what President Joe Biden called an "unprovoked and unjustified attack" on Ukraine — has even surfaced a wellspring of dissent in Russia, where publicly protesting the Kremlin can lead to retaliation.