Activists shouting slogans Thursday during a Strategy 31 rally in defense of the constitutional right to assembly.
Police detained dozens of opposition activists, including writer and politician Eduard Limonov, during a Strategy 31 rally Thursday on downtown's Triumfalnaya Ploshchad.
Also, an amendment before the State Duma aims to forbid the wearing of masks at rallies and would increase fines for protesters.
Strategy 31 rallies are held on the 31st day of each of the seven months with 31 days. The rallies are held in support of the Constitution's Article 31, which grants the right to free assembly.
The rallies, which have taken place since 2009, have never received permission from City Hall and are often broken up with a series of arrests.
Limonov, a prominent opposition figure, was able to walk only several meters before being detained, his spokesman, Alexander Averin, said. Other activists attempting to enter the square were promptly dispersed.
The event was marked by an increased police presence as officials gear up for larger protests planned for the Russia Day public holiday June 12.
On Wednesday, Moscow's Basmanny District Court sanctioned the arrest of two participants in May 6 protests who investigators said were assaulting police, RIA-Novosti reported.
Investigators said suspect Andrei Barabanov, 22, has ties to a violent anarchist movement. Barabanov denied that claim and said he was at the rally only to protect his girlfriend.
Suspect Maxim Luzyanin, 36, whose muscular physique appeared in striking contrast with the thin frame of Barabanov, was accused of attempting to strangle a police officer.
That officer, however, was not able to identify Luzyanin. The perpetrator was wearing a balaclava during the altercation.
Barabanov went on hunger strike to protest his arrest. He and Luzyanin will remain incarcerated until their trials, which are slated for July 6.
On Thursday, prosecutors issued a formal warning to Duma Deputy Dmitry Gudkov, who represents the left-wing A Just Russia party, for attempting to interfere with police at a May 6 rally, the Prosecutor General's Office said on its website.
The wearing of balaclavas and other masks during rallies may become illegal under new amendments backed by the ruling United Russia party.
The amendments, which also propose increased fines for participants and organizers of rallies, have passed their first of three readings in the Duma.
The legislation would also punish those who disseminate information about unsanctioned meetings via social networks, Vedomosti reported Thursday.
The public is divided over the plans to increase fines for participating in unsanctioned rallies.
In a recent state-endorsed survey, 41 percent of respondents did not support the idea.