Police in the Russian capital Moscow have detained some 300 people at an unauthorised protest against the exclusion of many opposition candidates from forthcoming local elections.
Protesters were dragged away from the city hall while others were corralled into nearby streets.
Some of the barred prospective candidates were detained earlier as police carried out searches.
The opposition say their candidates were barred for political reasons.
Officials disqualified about 30 people, saying they had failed to collect enough valid signatures to stand in the September 8 elections.
Moscow’s Mayor, Sergei Sobyanin, has called the demonstration a “security threat”, and promised to maintain public order.
Anger is widespread among opposition supporters at the way the city is run and the ruling United Russia party.
Opposition leader Alexei Navalny, a fierce critic of President Vladimir Putin, was jailed for 30 days on Wednesday after calling for Saturday’s unapproved demonstration.
Last Saturday, more than 20,000 Russians took to the streets, demanding fair elections, and dozens were arrested.
It is unclear how many people turned up for the new unauthorised rally on July 27 but the numbers seem to have been sharply down.
According to police, about 3,500 people gathered, including about 700 journalists.
Police in riot gear pushed back the crowd from barriers surrounding the mayor’s office in central Moscow, hauling off detainees to police stations.
A non-governmental monitoring group, OVD-Info, has reported at least 520 arrests while police put the figure at 295.
Local elections usually attract little attention in Russia.
The Moscow authority does not control the city’s budget or choose key official appointments, and previous votes have passed without major protests or press interest.
But this year some Muscovites are infuriated at what they see as brazen attempts to disqualify independent politicians from running.
Candidates were asked to collect 5,000 signatures to stand. This limit was made even harder to match because a signature “means volunteering one’s personal information for the government’s database of opposition supporters”, democracy activist Vladimir Kara-Murza wrote in the Washington Post.
Many candidates managed to meet the threshold but the electoral commission ruled some signatures ineligible, saying they were unclear or the addresses provided were incomplete, and barred the candidates from taking part.
