Demonstrators demanded the release from prison of Kremlin-critic Alexei Navalny, who has been on a hunger strike for three weeks. The marches swept across dozens of cities.
The main Russian opposition figure, who has been on a 20-day hunger strike, has been moved to an infirmary at another prison, where he will undergo "vitamin therapy," authorities say.
Doctors traveled to the penal colony where Navalny is imprisoned and were arrested outside its gates. Navalny is on a hunger strike to protest a lack of medical care.
After weeks of protests and crackdowns, allies of the opposition figure Alexei Navalny urged Russians to hold up their phones outside for spans of 15 minutes.
Foreign Minister Sergei Lavrov said in an interview "We don't want to isolate ourselves from global life, but we have to be ready for that. If you want peace then prepare for war,"
NPR's Scott Simon remarks on the sentencing this week of Russian opposition leader Alexei Navalny. The Putin critic was poisoned last year, recovered in Germany, then arrested for violating parole.