The protest was held in front of the Ministry of Economic Development.
About 10 activists protested a 34 percent increase introduced this year in mandatory insurance fees for small business owners.
Police said that Mitrokhin was detained as the protest organizer after the demonstrators resorted to actions for which they had not received formal permission from the municipal authorities.
The protesters released three large balloons marked: "President," "State Duma," and "Ministry of Economic Development" attached to a paper figure symbolizing a vendor with a figure "34" drawn on his back.
Some 200 vendors had traveled to Moscow from different parts of the Russian Federation to stage protests against the mandatory insurance fees increase, taxation, and perceived unfair positions of large supermarkets and stores in Russian towns and cities.
May 26 is marked annually in Russia as the Day of Entrepreneurs.
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