MOSCOW, January 1 (RIA Novosti) - Russian police have released all participants of an unsanctioned protest rally detained on December 31 in downtown Moscow’s Triumfalnaya Square, the Interior Ministry reported on Tuesday.

“All detainees have been released,” the ministry said.

On Monday, it was reported that police detained some 25 protesters, including writer and radical protest leader Eduard Limonov, the head of the unregistered Other Russia party, at a traditional Strategy-31 protest rally.

"About 50 people took part in the unsanctioned action on Triumfalnaya Square, which is just one-fourth the number that took part on December 31 last year," a police spokesman told RIA Novosti on Monday.

Russian opposition groups rally 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.

They had filed an application to hold a sanctioned meeting, but City Hall rejected their request, citing the legal violations committed by the applicants at previous unsanctioned rallies.

The chief of police in central Moscow had warned the organizers earlier against holding the unsanctioned protest.