Police detained about 10 activists at a Moscow demonstration in support of jailed oil tycoon Mikhail Khodorkovsky on Sunday, his 48th birthday and eighth behind bars.
Around 50 activists wearing red T-shirts with Khodorkovsky's portrait on them marched down the Old Arbat pedestrian street handing out shirts and balloons.
Suddenly from the rooftop of a building along their route, a large plastic banner wishing Khodorkovsky a happy birthday and freedom unfurled, spilling leaflets onto the street. Firecrackers went off on the roof.
Police detained about 10 of the activists, who were then driven away in police vehicles.
A demonstration also was held Sunday in St. Petersburg and another was planned in London.
Khodorkovsky has been in prison since his arrest in 2003 on charges seen as punishment for challenging the power of Vladimir Putin, who was president at the time and is now prime minister. A second conviction late last year will keep Khodorkovsky incarcerated until 2016 unless he is granted parole.
"We are here because we have political prisoners in our country and we don't want to have them," St. Petersburg opposition leader Olga Kurnosova told a crowd of about 100 people. She spoke in front of a banner reading: "The prison sentence for Khodorkovsky is a prison sentence for the future of Russia."
The demonstrators wished Khodorkovsky a happy birthday and chanted "Freedom, freedom." Police stood by, allowing the protest rally to take place.
Khodorkovsky, once Russia's richest man, has won admiration from some of his countrymen for his refusal to bend. For his supporters, he has become a symbol of the corruption and other excesses under Putin.
Many Russians, though, have little sympathy for Khodorkovsky, who was one of a small circle of politically connected businessmen who grew fabulously wealthy after taking over state companies in the 1990s.
Irina Titova in St. Petersburg, Russia, contributed to this report.