Frustration over the exclusion of opposition candidates from Moscow’s local election next month drew tens of thousands of protesters on Saturday, making it the city's largest protest rally in eight years, by some estimates.

The rally marked the fourth consecutive weekend of demonstrations of the Russian capital’s city council ballot. The demonstration has prompted protests in other cities, reflecting wider frustrations with Russia's tightly controlled politics.

Unlike the previous two Moscow rallies, where police harshly dispersed the crowds and arrested more than 1,000 protesters, Saturday's gathering was officially sanctioned.

Beliy Schetchik, a group that monitors attendance of public meetings, said it counted about 50,000 people at the demonstration, but police put that figure at 20,000.

After the rally, hundreds of participants streamed to an area near the presidential administration building to continue with an unauthorized demonstration and were confronted by riot police.

OVD-info, an arrest-monitoring group, said 136 people were detained. The group also said that 86 people were arrested in St. Petersburg at an unsanctioned demonstration in support of the Moscow protests.

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Some opposition figures called for an unauthorized march to follow the permitted rally, but it was unclear if the action would materialize.

Russia’s most prominent opposition leader, Alexei Navalny, remains in jail for breaking protest law. Late last month, he was transferred to a hospital from his detention facility for a condition one physician said was consistent with poisoning.

Lyubov Sobol, one of the city council candidates denied a place on the ballot and a spearhead of the election protest, was arrested before Saturday’s rally, Reuters reported.

“I won’t make it to the protest. But you know what to do without me…Russia will be free!” Sobol wrote on Twitter.

A video on Sobol's Twitter feed showed officers breaking into her office as she demanded an explanation from them.

Small related protests also were reported in several Siberian cities on Saturday.

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Senators in Russia’s upper-house Federation Council said Friday they will draft legislation to further restrict where citizens can protest, The Moscow Times reported.

The Associated Press contributed to this report.