Camouflage-clad riot police have detained around 20 protesters who were trying to hold an anti-Kremlin demonstration in central Moscow.

Moscow's City Hall refused to give permission for the rally on Triumfalnaya Square, saying a sports event had already been scheduled for the same time and place. Authorities generally refuse permission for any opposition gatherings to be held in central or highly visible areas.

Demonstrators arrived Friday on the scene in small groups and many were seized by police and hustled away quickly.

None of Russia's high-profile opposition activists were seen in attendance.