Police have detained more than 500 people at rallies in Siberia and Russia's far east as supporters of Kremlin critic Alexei Navalny took to the streets to protest his jailing, despite biting cold and the threat of arrest.
The rallies, also set to take place in Moscow and other cities later on Sunday, follow large protests last weekend and are part of a campaign to pressure the Kremlin into freeing President Vladimir Putin's most prominent opponent.
The opposition politician was arrested on January 17 after returning to Moscow from Germany where he had been recovering from a nerve-agent poisoning in Russia last summer.
He accuses Putin of ordering his murder, which the Kremlin denies.
Police have said the protests have not been authorised and will be broken up, as they were last weekend when more than 4000 people were detained, according to OVD-Info, a protest monitoring group.
In the far eastern city of Vladivostok police prevented protesters from accessing the centre, forcing them to relocate to the waterfront.
Video footage showed protesters chanting "Putin is a thief" as they linked hands and marched on the ice in temperatures of around -13C.
In Tomsk, the Siberian city that Navalny visited before suddenly collapsing on a domestic flight last August, demonstrators gathered in front of a concert hall chanting "Let him go" and holding up Russian flags.
Dozens of people in the east Siberian city of Yakutsk turned out in temperatures of -42C.
"This is the first time I've come to a protest. I'm just fed up with the total lawlessness of the authorities," Ivan, a protester who declined to give his surname, said.
The protest is a test of Navalny's support after many of his prominent allies were targeted in a crackdown this week. Several, including his brother Oleg, are under house arrest.
"If we stay quiet, then they could come for any of us tomorrow," Navalny's wife, Yulia Navalnaya, wrote on Instagram.
In Moscow, police deployed in force before the rally, sealing off the planned protest location to pedestrians and closing several metro stations.
Navalny, 44, is accused of parole violations which he says are trumped up.
A court is due to meet next week to consider handing him a jail term of up to three-and-a-half years.
The West has told Moscow to let Navalny go and his allies have appealed to US President Joe Biden to impose sanctions on 35 people they say are Putin's close allies.