In Moscow, around 2,000 people joined a protest in support of jailed opposition activist Sergeï Uldaltsov on Thursday.
The head of Russia’s Left Front movement has been put in prison 14 times this year, most recently ahead of the legislative elections on December 4.
Udaltsov has made three court appearances since then and each time his jail term has been extended.
His supporters say the reasons for prolonging his sentence have been falsified.
“The last case in which Udaltsov was imprisoned was totally fabricated,” said opposition leader Vladimir Ryzhkov. “Lawyers, human rights groups, interior ministry observers – they all say that.
“This is absolute lawlessness. It’s a disgrace and there are many other people like him around the country,” Ryzhkov added.
There were fears that Moscow police would crack down on the protests, which organisers presented as a meeting with one of the members from Russia’s Duma, the lower house of parliament.