"The detainees attempted to stage an unauthorized event, and were promoting narcotics," a spokesperson for Moscow's Interior Department said, adding that administrative cases could be opened against them.
According to the Russian Interior Ministry's chief communications officer, Valery Gribankin, police had credible information that participants would use the rally to peddle drugs to members of the public.
Moscow's security chief, Nikolai Kulikov, said Friday the municipal government had rejected a request to allow "legalize marijuana" parades in the city this weekend and that any such rallies would be dispersed as unauthorized.
The parades have been intended as part of the Global Marijuana March, held every May since 1999 in more than 400 cities across the world.
Attempts to stage events promoting cannabis culture were made in Moscow in previous years, but all such actions were cracked down on by authorities.
