Yulia Navalnaya, the wife of the Kremlin critic Alex Navalny, is among more than 1,600 arrested during demonstrations for his release from detention, reports said Sunday.
Navalnaya was detained in Moscow on the sidelines of a protest held in support of the Russia opposition leader, the OVD-info monitoring group said.
Navalny was recently arrested after he flew back to Russia from Germany. He had spent the past five months recovering from a nearly fatal nerve agent-attack in August, the BBC reported.
The 44-year-old lawyer is in detention pending four legal matters he said were "trumped up." He accused Russian President Vladimir Putin of ordering his attempted murder. Putin has denied the accusation and said Navalny was part of a U.S.-supported dirty-tricks campaign to discredit him.
Earlier, Navalny's supporters used social media to call for unauthorized rallies supporting Navalny. Police warned against attending illegal rallies and said any attempts to hold events - as well as any provocations by the participants - would be considered a threat to public order.
Russia authorities have detained more than 3,000 and used force to break up protests across the country as tens of thousands of demonstrators ignored extreme cold and warnings to demand the release of Navalny.
In central Moscow, where an estimated 40,000 protesters had assembled in one of the largest unsanctioned rallies in years, police were seen detaining people and bundling them into nearby vehicles.
Riot police were deployed with news media reporting detentions in Khabarovsk and Vladivostok. In Novosibirsk, there were chants of "Putin is a thief."
Navalnaya posted an image of herself on Instagram saying: "Sorry for the poor quality. Very bad light in the paddy wagon," Business Insider reported. Navalny's mother, Lyudmila Ivanovna Navalnaya, also joined the protest in Moscow.
Her lawyer was not allowed to accompany her to the police van. She was released after several hours in custody.
Authorities have arrested and detained several allies of Navalny as a result of the demonstrations, including his representative Kira Yarmysh, Anti-Corruption Foundation investigator Georgy Alburov and opposition activist Lyubov Sobol.
Navalny's Anti-Corruption Foundation released a document that claimed Putin secretly built a palace worth $1 billion near Gelendzhik on the Black Sea bankrolled by bribes. The Kremlin denied this.