Russian police have arrested more than 2,000 people and used force to break up rallies around the country, a monitoring group said, as tens of thousands of protesters demanded the release of Kremlin critic Alexey Navalny, whose wife was among those detained.

Navalny had called on his supporters to protest on Saturday after being arrested last weekend as he returned to Russia from Germany for the first time since being poisoned with a nerve agent he says was applied to his underpants by state security agents in August.

The authorities had warned people to stay away from the protests, saying they risked catching COVID-19 as well as prosecution and possible jail time for attending an unauthorised event. But protesters defied the ban and bitter cold and turned out in force.

The OVD-Info protest monitor group said at least 2,131 people – including 300 in the capital, Moscow and 162 in Saint Petersburg – had been detained across Russia, a number likely to rise. It reported arrests at rallies in nearly 70 towns and cities.

In central Moscow, where an estimated tens of thousands of people had gathered in one of the biggest unauthorised rallies for years, police were seen detaining people, bundling them into nearby vans. The authorities said just some 4,000 people had shown up.

Navalny’s wife, Yulia, said on social media she had been detained at the rally. She was later released. Lyubov Sobol, a prominent aide of Navalny and lawyer, was also among those held.

Video footage from Vladivostok showed riot police chasing a group of protesters down the street, while demonstrators in Khabarovsk, braving temperatures of about -14C (7F), chanted “Shame!” and “Bandits!”

Police in the Siberian city of Yakutsk, one of the coldest cities in the world and where the temperature was -52C (-61.6 Fahrenheit) on Saturday, grabbed a protester by his arms and legs and dragged him into a van, video footage from the scene showed.

Navalny, 44, is in a Moscow prison pending the outcome of four legal matters he describes as trumped up. He could face years in jail. Authorities accused him of violating the terms of a suspended sentence in a 2014 conviction for financial misdeeds, including when he was convalescing in Germany.

But Navalny accuses President Vladimir Putin of ordering his attempted murder. Putin has dismissed that, alleging the 44-year-old is part of a United States-backed dirty tricks campaign to discredit him.

Following Navalny’s arrest, his team released an investigation into a lavish Black Sea property allegedly owned by Putin, a claim the Kremlin denied.

The two-hour video report has been viewed more than 64 million times since its release on Tuesday, becoming the Kremlin critic’s most-watched YouTube investigation.

Navalny’s arrest drew widespread Western condemnation, with the US, the European Union, France and Canada all calling for his release.