More than 500 people have been detained as rallies in support of jailed opposition leader Alexei Navalny begin across Russia, a monitoring group says.
In Moscow police have closed metro stations and are restricting movement in the city centre. About 100 people have been detained there, Reuters says.
Mr Navalny was jailed on his return to Russia after recovering from an attempt to kill him with a nerve agent.
He is accused of not complying with a suspended sentence.
Mr Navalny had only just arrived from Berlin, where he spent months recovering from the near-fatal attack.
Russian authorities say he was supposed to report to police regularly because of a suspended sentence for embezzlement.
Mr Navalny has denounced his detention as “blatantly illegal”, saying the authorities knew he was being treated in Berlin for the Novichok poisoning, which happened in Russia last August.
What’s the latest?
Rallies in support of Mr Navalny have already taken place in the east of Russia, despite police warnings about gatherings.
In the Siberian city of Novosibirsk, at least 2,000 people marched through the city chanting “Freedom” and “Putin is a thief”.
In Yakutsk, where temperatures fell to -40C, a protester named Ivan said it was the first rally he had attended.
“I am tired of the despotism and lawlessness of the authorities. No questions have been answered. I want clarity, openness, and change. This is what made me come here,” he said.
Further rallies saw about 1,000 people demonstrate in Omsk, also in Siberia, and about 7,000 people rally in Yekaterinburg in the Ural region, according to local media reports.
Police have detained 519 people, according to the OVD-Info protest monitoring group.
Protests in Moscow are due to take place later.
A number of close associates of Mr Navalny have been detained since last week and others, including his brother and Pussy Riot activist Maria Alyokhina, have been put under house arrest.
Tight security in Moscow this morning. Just saw long lines of police vans parked by Pushkin Square and near FSB HQ & Presidential Administration. Police plan to block off whole area around the Kremlin. Authorities doing all they can to prevent Navalny supporters from gathering.
— Steve Rosenberg (@BBCSteveR) January 31, 2021
The chief editor of a Russian website specialising in human rights, Sergei Smirnov, was also arrested outside his home on Saturday. News of his detention, apparently over allegations he participated in last week’s protests, has been condemned by other journalists.
In Moscow, police have reportedly been struggling to find space in jail for supporters of the opposition leader.
Seven metro stations will be closed in Moscow on Sunday and movement of pedestrians will be limited in the city centre, the AFP news agency reports.
Protesting on ice. In Vladivostok they’re shouting ‘My Russia is in prison!’
Numbers today may well be lower: the risk of protesting is v high-from probs at work/college or a few days’ detention to full-on criminal prosecution. But the protest mood is clearly growing here. https://t.co/kjlcfdBCp4
— Sarah Rainsford (@sarahrainsford) January 31, 2021
Mr Navalny blamed state security agents under Mr Putin’s orders for the Novichok attack which nearly killed him. Investigative journalists from the Bellingcat website have named Russian FSB agents suspected of the poisoning.
The Kremlin denies involvement and disputes the conclusion, by Western weapons experts, that Novichok was used.