Hundreds of protesters were violently arrested in Moscow on Saturday for the second week running at a demonstration calling for fair elections.
Independent watchdog OVD-Info said at least 838 people were detained. The Russian Interior Ministry said the number was about 600, according to The Associated Press.
Opposition leader Lubovj Sobol was among the jailed.
Authorities had warned that all necessary measures would be taken to stop the unsanctioned protest. Demonstrators said they wanted to march in the center of Moscow but they met with police in riot gear who were deployed in large numbers. Internet and cellular connection were also appeared to have been cut in the center of the city and human rights activists said lawyers were not allowed to meet with those who were arrested.
Last week police cracked down and arrested 1,400 people at a demonstration called by the same organizers.
These protests were sparked by authorities' refusal to allow opposition candidates to take part in Moscow's city council elections. But they have taken on a broader significance, viewed as a sign of the Kremlin's growing intolerance for even low-level political opposition.
Another opposition rally is scheduled for next Saturday.