Russian opposition leader Alexei Navalny has been freed after a brief spell in police detention in Moscow as thousands rallied against a March election expected to extend Vladimir Putin's Kremlin term. "I'm free," Navalny said on Twitter late yesterday, adding: "Today has been an important day. Thanks to all those who were not afraid to fight for their rights." Heeding a call by Putin's bete noire, thousands braved freezing temperatures to stage rallies in dozens of cities to protest upcoming "pseudo-elections," as Navalny and his supporters refer to them. In Moscow, Navalny chanted "Swindlers and thieves" at a rally in the city centre Sunday before several police officers pounced on the 41-year-old opposition politician, knocking him to the ground and dragging him on to a bus. Authorities said earlier Navalny would be charged with organising an unpermitted protest, adding he had been taken to a police station. The opposition leader urged Muscovites not to give up. "You are not rallying for me, but for yourselves and your future," he tweeted. About 4,000 people turned up for the unsanctioned rally in Moscow, with many chanting "Down with the czar" and brandishing placards saying "Voters' strike." Authorities beefed up security, dispatching police vans and passenger buses to the city centre, but police largely refrained from arresting protesters. A crowd of protesters was later allowed to walk down to Red Square. One group of protesters walked several kilometres and reached the government headquarters as police watched on. Authorities estimated the Moscow turnout at around 1,000 people. Ahead of the Moscow rally police broke into Navalny's headquarters using a power saw. Police also detained several members of Navalny's team. More than 250 people were detained across the country, according to OVD-Info, an independent monitor. Yesterday's turnout paled in comparison to last year's protests when tens of thousands demonstrated against corruption among Russia's elite in March and June, 2017. Police unleashed a severe crackdown afterwards, arresting more than 1,000 people including schoolchildren. Navalny himself served three jail sentences of 15 days, 25 days and 20 days for organising unauthorised protests last year.