Opposition leaders cried foul after Moscow's election commission said most of their sponsored candidates failed to secure the required number of signatures to participate in the election as candidates.
The commission has yet to officially announce the list of legitimate candidates for the 8 September vote to the 45-seat parliament.
Ilya Yashin, a critic of President Vladimir Putin, and several other activists had called for a meeting with the voters on Sunday, which transformed into a march to the Moscow city mayor office and then to the headquarters of the election commission.
Mr Yashin said the election commission's allegation that many of the signatures supporting him were rigged was an "absolute fraud".
The participants shouted anti-government and anti-Putin slogans, urging the authorities to register their candidates.
The police have not resorted to force to disperse the crowd, as it had many previous opposition rallies.
There is a history of anti-Kremlin activists being denied access to run for the parliament seats or presidential office.
Alexei Navalny, a prominent opposition leaders, was barred from running in the 2018 presidential election after officials ruled he was ineligible to take part due to a suspended prison sentence.
The Moscow city election commission was not available for comment on Sunday.
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