Moscow police have quickly broken up a protest of a few dozen opposition activists and detained about 30 participants.
The action, dubbed the "Day of Wrath," was organized by Left Front, whose leader Sergei Udaltsov is currently serving a 15-day jail sentence for taking part in an unsanctioned rally July 31.
A few dozen protesters gathered on Friday outside the Teatralnaya metro station near the Kremlin, chanting "Free Sergei Udaltsov!" and some of them lay down on the ground. Police dispersed the demonstrators within minutes.
Amnesty International has declared Udaltsov a prisoner of conscience and demanded his immediate release.