Russian police have raided the offices and apartments of opposition leader Alexei Navalny, who has been jailed since returning to the country on January 17.
Kremlin critic Navalny was arrested as he came back to Russia for the first time since being poisoned by the nerve agent Novichok.
Navalny, 44, was taken ill on a flight from Siberia to Moscow in August. He was later transferred to a clinic in Germany where he spent five months recovering.
He blames the regime of Russian President Vladimir Putin for the poisoning. The Kremlin has denied responsibility.
After his arrest in mid-January, Navalny called on supporters to take to the streets and protest, and the country has seen demonstrations held nationwide. Last weekend around 4,000 people were reportedly detained by police during protests.
On Wednesday his aides reported that police had raided his Moscow apartment, another residence where his wife is living, and offices of his anti-corruption organisation.
Members of his team posted evidence of the raids on social media.
It was not immediately clear whether anyone had been arrested.
Leonid Volkov, head of Navalny's corruption-investigating organisation, said the searches were being carried out for alleged epidemiological or sanitary violations.
Police also searched the apartment of Navalny's spokeswoman and an investigator for Navalny's group, the organisation reported.
Crackdown on social media
It came as Russia’s media monitoring agency Roskomnadzor announced sanctions on social media giants Facebook, Instagram, Twitter, TikTok, VKontakte, Odnoklassniki and YouTube for allegedly allowing people to incite others to protest in support of Navalny.
Asked about Saturday's protests, Putin said that “all people have the right to express their point of view within limits, outlined by law".
“They also came out with political slogans. But outside the law. Why should everything outside the law be allowed here? No,” Putin said.
The Russian protests and crackdown appeared to have further strained Russia-US relations.
US State Department spokesman Ned Price on Saturday condemned “the use of harsh tactics against protesters and journalists” and urged authorities to release Navalny and "all those detained for exercising their universal rights.”
Kremlin spokesman Dmitry Peskov accused Washington of interfering with Russia's “internal affairs," after the US Embassy in Moscow put a warning on its website detailing times and places of rallies in different Russian cities and urging US citizens to avoid them.