More than 280 people were detained in Moscow for protesting a court hearing that decides if Navalny should be jailed for violating the terms of a suspended sentence he was given on embezzlement charges in 2014.
Russian opposition leader Alexey Navalny has denounced a Moscow court that is considering whether he should be sent to prison for years.
The Kremlin critic on Tuesday called the hearing a vain attempt by Moscow to scare millions of Russians into submission.
Speaking from a glass cage in the courtroom, Navalny attributed his arrest to Russian President Vladimir Putin’s “fear and hatred," saying the Russian leader will go down to history as a “poisoner.”
“I have deeply offended him simply by surviving the assassination attempt that he ordered,” he said.
“The aim of that hearing is to scare a great number of people,” Navalny said. “You can't jail millions. You can't jail the entire country."
A judge in Moscow will decide on Tuesday whether Navalny should be imprisoned for violating the terms of a suspended sentence he was given on embezzlement charges in 2014.
The money-laundering conviction is widely seen as politically motivated.
Navalny's team called for a demonstration outside the Moscow court building but police were out in force near the building, cordoning off the nearby streets and making random arrests.
Police in full riot gear cordoned off the courthouse and arrested several dozen people outside.
OVD-Info, a group that monitors arrests and opposition protests, said more than 280 people including journalists had been seized by police.
Last month, Russia's prison service filed a motion to replace Navalny's 3 1/2-year suspended sentence from the conviction with one he must serve.
The Prosecutor General's office backed the motion alleging Navalny engaged in "unlawful conduct" during the probation period.
Navalny's jailing has triggered massive protests across Russia over the past two weekends, in which tens of thousands took to the streets to demand his release, chanting slogans against Putin.
Police detained over 5,750 people during Sunday's rallies, including more than 1,900 in Moscow, the biggest number the nation has seen since Soviet times. Some were beaten.
The jailing of Navalny and the crackdown on protests have stoked international outrage, with Western officials calling for his release and condemning the arrests of demonstrators.
The Kremlin said on Tuesday it hopes the fate of jailed opposition Navalny would not affect Russia's ties with Europe.
"We hope that such nonsense as linking the prospects of Russia-EU relations with the resident of a detention centre will not happen," Kremlin spokesman Dmitry Peskov told reporters.
The court hearing and Peskov's comments come days ahead of a visit to the Russian capital by the European Union's foreign affairs chief Josep Borrell.
The Spanish diplomat is expected to raise Navalny's detention during talks with Russian Foreign Minister Sergei Lavrov on Friday.