According to figures published today on its website, “more than 101 people were arrested in ten cities, most of them in St Petersburg”.
Throughout the night, floral tributes to Navalny placed near several memorials were removed by unidentified people as police watched, videos and photos posted on social media reveal.
In Moscow, tributes were removed from a memorial next to the headquarters of the Russian security services, but flowers were back at the site in the morning.
On Saturday, police blocked access to a memorial in the Siberian city of Novosibirsk and detained several people, according to OVD-Info.
Russian dissident Alexei Navalny, one of Vladimir Putin's leading critics, has died in prison, Russia's Federal Prison Service said.
Navali, 47, was in a prison in the Arctic, serving a 19-year sentence under a “special regime,” and according to the services, he fell ill after a walk and lost consciousness.
So far, Navalny's team has not confirmed the information, but prominent Western leaders and supporters of the opposition blame Russian President Vladimir Putin for his death.