MOSCOW -- Police in Moscow have detained the leader of the unregistered Libertarian Party, Sergei Boiko, and activist Mark Galperin for their roles in an unsanctioned rally in the Russian capital on August 31.
The two opposition activists were detained on September 3, their colleagues said.
Members of the Libertarian Party said Boiko was detained for announcing via the Internet the rally against political repression.
Galperin's lawyer, Nikolai Zboroshenko, said that his client was detained for participating in the rally.
The day before, police in Moscow detained Novaya gazeta journalist Ilya Azar, former Moscow city-council candidate Lyubov Sobol, and opposition activist Nikolai Lyaskin.
All three took part in the August 31 rally as well. They were charged with violating regulations on organizing public gatherings and released hours later and hearings into the cases are pending.
The August 31 rally was the latest in a series of confrontations between liberal activists and Moscow city authorities -- and the Kremlin.
Demonstrators clapped and chanted "Russia will be free!" and "Down with the tsar!" as they walked along a leafy boulevard just a few kilometers north of the Kremlin.
Sobol led people chanting "Freedom for political prisoners."
"People of different ages have come out because everyone wants justice. They want Russia to be free and happy and to not drown in lawlessness and mayhem. We demand this and we will not back down," she told reporters.
Neither police nor independent watchdogs reported any arrests or detentions during the demonstration -- in contrast to other recent protests in which thousands were detained, sometimes violently.
Police said about 750 assembled in Moscow that day.
Several opposition leaders were detained ahead of the August 31 event, including opposition politician Ilya Yashin, who has struggled to register for the election. He was detained on August 28 immediately after he completed a fourth 10-day jail term on similar charges of attending unauthorized rallies.