Russian authorities have arrested more than 10,000 people in recent opposition protests, according to observers.
Arresters are sometimes locked up for hours without food or the possibility to use a toilet, an analyst from protest monitor group OVD-Info told radio station Ekho Moskvy.
Supporters of Navalny, a known opponent of President Vladimir Putin, have taken to the streets for the past two weekends to demand his release.
Supporters of the politician also demonstrated in Moscow on Tuesday evening. This happened after the court had sent the opposition leader to a penal colony for 2.5 years.
Russian authorities have repeatedly warned that the protests are illegal. The Kremlin on Wednesday called the actions of the riot police in the protests justified.
