More than 2,500 people were arrested after protests were held across Russia demanding the release of jailed opposition leader Alexei Navalny.
In Moscow, about 15,000 demonstrators gathered in the city centre, where clashes with police broke out.
Nationally, tens of thousands answered Mr Navalny’s protest call to rally, issued after he was detained at Moscow airport on arrival from Germany, where he had been recovering from a near-fatal poisoning with a nerve agent.
Last month, Mr Navalny released the recording of a phone call he said he made to a member of a group of officers from the Federal Security Service, who he claimed poisoned him in August, then tried to cover it up. The FSB dismissed the recording as fake. Russia denied having anything to do with his poisoning.
Saturday’s protests spanned more than 100 cities across the country, AFP reported.
Moscow city leaders had warned Mr Navalny’s supporters to stay away from the protests, saying they risked prison sentences for attending an unauthorised event, and the risk of contracting Covid-19.
When police pushed demonstrators out of Moscow’s Pushkin Square, many of them regrouped along a wide boulevard about a kilometre away.
Some later went to protest near the jail where Mr Navalny is held. Police made an undetermined number of arrests there. The anti-corruption campaigner’s wife, Yulia, was among those detained.
The US called for Mr Navalny’s “immediate and unconditional” release.
Britain’s foreign ministry said it was “deeply concerned by the detention of peaceful protesters”.
