Human rights activists rally in Triumfalnaya Square the last day of each month with 31 days in observance of the often-ignored Article 31 of the Russian Constitution, which guarantees freedom of assembly.
A group of activists led by Lyudmila Alexeyeva of the Moscow Helsinki Group applied for a rally of 1,500 people, but the authorities allowed only 1,000, and only 500 showed up. They were surrounded by 2,000 police officers, RIA Novosti reported.
The protest went smoothly until several dozen supporters of Limonov's Other Russia party gathered for an unsanctioned protest nearby.
Twenty of them, including Limonov, were arrested, said police spokesman Viktor Biryukov.
In St. Petersburg, 60 demonstrators were detained.