Policemen detained 24 people at an unsanctioned rally in downtown Moscow on Tuesday, a spokesman for the Moscow police said.
"Twenty four people were detained on Triumfalnaya Square in Moscow for an attempt to hold a rally that was not sanctioned by the authorities," the spokesman said.
The protesters chanted anti-government slogans and handed out leaflets. The detained were taken away in two police buses.
Russian opposition groups regularly rally on the Triumfalnaya Square on the last day of each month that has 31 days in defense of their right to freedom of assembly, as enshrined in Article 31 of the Russian Constitution.