A couple sit in a boulevard as police walk to prevent protesters during a rally in Moscow, Russia, Saturday, Aug. 10, 2019. Tens of thousands of people rallied in central Moscow for the third consecutive weekend to protest the exclusion of opposition and independent candidates from the Russian capital's city council ballot. (AP Photo)

MOSCOW (AP) — Tens of thousands of people rallied Saturday against the exclusion of some city council candidates from Moscow's upcoming election, turning out for one of the Russian capital's biggest political protests in years.

After the rally, which was officially sanctioned, hundreds of participants streamed to an area near the presidential administration building to continue with an unauthorized demonstration. They were confronted by phalanxes of riot police and the arrest-monitoring group OVD-Info said 136 people were detained.

The rally was the fourth consecutive weekend demonstration in Moscow over the local election. The determined opposition has prompted protests in other cities, reflecting widespread frustration with Russia's tightly controlled politics.

The protest attracted some 50,000 people, said Beliy Schetchik, an organization that counts public meeting attendance.

OVD-Info also said 86 people were arrested Saturday in St. Petersburg at an unsanctioned demonstration in support of the Moscow protests.

Unlike the previous two Moscow rallies, where police harshly dispersed the crowds and detained thousands of demonstrators, Saturday's gathering in a neighborhood with relatively few passers-by was officially sanctioned.

It was held on a street flanked by high buildings and sandwiched between two busy thoroughfares.

Lyubov Sobol, one of the city council candidates denied a place on the ballot and a spearhead of the election protest, was among those detained in Moscow on Saturday.

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.

People with posters show portraits of detained protesters and a boy with a poster reads Lyubov Sobol react during a protest in Moscow, Russia, Saturday, Aug. 10, 2019. Tens of thousands of people rallied in central Moscow for the third consecutive weekend to protest the exclusion of opposition and independent candidates from the Russian capital's city council ballot. (AP Photo/Alexander Zemlianichenko)
In this pictures taken from the Associated Press Television footage, police officers detain Russian opposition activist Lyubov Sobol near her office in Moscow, Russia, Saturday, Aug. 10, 2019. Police on Saturday detained Lyubov Sobol, one of the city council candidates denied a place on the ballot and a spearhead of the election protest. (AP Photo/Francesca Ebel)
People with national flags and various political parties flags gather during a protest in Moscow, Russia, Saturday, Aug. 10, 2019.  Masses of people gathered in central Moscow to demand that opposition candidates be included on ballots for an upcoming city parliament election in September. (AP Photo/Alexander Zemlianichenko)
A woman looks at police as they walk to block demonstrators during a protest in Moscow, Russia, Saturday, Aug. 10, 2019. Tens of thousands of people rallied in central Moscow for the third consecutive weekend to protest the exclusion of opposition and independent candidates from the Russian capital's city council ballot. (AP Photo)
Police detain a protester during a protest in Moscow, Russia, Saturday, Aug. 10, 2019. Tens of thousands of people rallied in central Moscow for the third consecutive weekend to protest the exclusion of opposition and independent candidates from the Russian capital's city council ballot. (AP Photo/Alexander Zemlianichenko)
People with posters show portraits of detained protesters and slogan reads
People with national flags and various political parties flags gather during a protest in Moscow, Russia, Saturday, Aug. 10, 2019.  Masses of people gathered Saturday in central Moscow to demand that opposition candidates be included on ballots for an upcoming city parliament election in September. (AP Photo/Alexander Zemlianichenko)
People with national flags and various political party flags gather during a protest in Moscow, Russia, Saturday, Aug. 10, 2019. Masses of people gathered in central Moscow to demand that opposition candidates be included on ballots for an upcoming city parliament election in September. (AP Photo/Alexander Zemlianichenko)
A woman holds a poster reading:
A protester holds a poster reading:
Members of Russian experimental electronic group IC3PEAK leave a protest after a performance in Moscow, Russia, Saturday, Aug. 10, 2019. Tens of thousands of people rallied in central Moscow for the third consecutive weekend to protest the exclusion of opposition and independent candidates from the Russian capital's city council ballot. (AP Photo/Alexander Zemlianichenko)
Youth protesters listen to a speaker during a protest in Moscow, Russia, Saturday, Aug. 10, 2019. Tens of thousands of people rallied in central Moscow for the third consecutive weekend to protest the exclusion of opposition and independent candidates from the Russian capital's city council ballot. (AP Photo/Alexander Zemlianichenko)
Police block the road as people with national flags and various political parties flags gather during a protest in Moscow, Russia, Saturday, Aug. 10, 2019. Tens of thousands of people rallied in central Moscow for the third consecutive weekend to protest the exclusion of opposition and independent candidates from the Russian capital's city council ballot. (AP Photo/Alexander Zemlianichenko)
A protester holds a poster reading:
A woman gestures as people with national flags and various political parties flags gather during a protest in Moscow, Russia, Saturday, Aug. 10, 2019. Tens of thousands of people rallied in central Moscow for the third consecutive weekend to protest the exclusion of opposition and independent candidates from the Russian capital's city council ballot. (AP Photo/Alexander Zemlianichenko)
People with national flags and various political parties flags gather during a protest in Moscow, Russia, Saturday, Aug. 10, 2019. Tens of thousands of people rallied in central Moscow for the third consecutive weekend to protest the exclusion of opposition and independent candidates from the Russian capital's city council ballot. (AP Photo/Alexander Zemlianichenko)
A woman holds a Russian national flag in front of police during a protest in Moscow, Russia, Saturday, Aug. 10, 2019. some thousands of people rallied in central Moscow for the third consecutive weekend to protest the exclusion of opposition and independent candidates from the Russian capital's city council ballot. (AP Photo)
Police detain a protester during a rally in Moscow, Russia, Saturday, Aug. 10, 2019. Tens of thousands of people rallied in central Moscow for the third consecutive weekend to protest the exclusion of opposition and independent candidates from the Russian capital's city council ballot. (AP Photo)
Police walk to block protester during a protest in Moscow, Russia, Saturday, Aug. 10, 2019. Tens of thousands of people rallied in central Moscow for the third consecutive weekend to protest the exclusion of opposition and independent candidates from the Russian capital's city council ballot. (AP Photo)