Russians vowed to protest in favour of candidates being allowed to run in elections.
Tens of thousands of people rallied Saturday in one of Moscow's biggest political protests in recent years, denouncing the exclusion of opposition and independent candidates from the capital's city council ballot.
A group that monitors attendance of public meetings, Beliy Schetchik, said it counted about 50,000 people at the demonstration; a police estimate put the crowd at 20,000.
The rally was the fourth consecutive weekend demonstration in Moscow over the local election.
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.
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Unlike the previous two Moscow rallies, where police harshly dispersed the crowds and detained thousands of demonstrators, Saturday's gathering in a neighbourhood with relatively few passers-by was officially sanctioned.
It was held on a street flanked by high buildings and sandwiched between two busy thoroughfares.
Riot police ringed off the presidential administration building after a crowd gathered nearby following an opposition rally and hundreds more were seen walking towards the area chanting, Reuters reported.
More than 500 people were seen moving towards the area, many of them young and chanting: "Putin is a thief".
Unsanctioned protests were planned in at least 40 cities to show support for Moscow despite the thousands of detentions in recent weeks. Independent monitors told Reuters that 275 people were detained by police across the country.
The demonstrations started after independent candidates were not allowed to run in an upcoming September election for the Moscow City Duma, the city's regional government.
Russian officials said they did not have enough genuine signatures in their support or in certain cases that there were mistakes in the election documents, according to independent Latvia-based Russian news aggregator Meduza. Candidates said those claims were false.
Video footage showed police officers beating protesters last weekend. It was the second weekend in a row that over 1,000 protesters were detained.
One of the main protest organisers updated their demands in a note on Facebook, stating that they wanted a release of political prisoners, "termination of absurd criminal cases" and the release of independent candidates.
They also demanded the resignation of several Moscow officials and an investigation into those "involved in the fabrication of criminal cases and violence against protesters".
"Previous rallies were mainly around the subject of the ban on independent candidates," said Alexander Baunov, a political expert at Moscow Carnegie Center.
Petr Verzilov, one of the organisers of the march, told Euronews before it began that the protest this had been fully authorised and that he expected a lot of people to show up.