Metal police barricades have been erected on the central Moscow square where the March of Dissent is planned.
Special police forces, the OMON, are being deployed to the capital.
Yulia Malysheva, one of the march's organizers, told RFE/RL's Russian Service that large numbers of OMON officers have already been deployed to Moscow from other regions. She expressed concern, saying that "regional OMON as a rule do not bear responsibility for their behavior in another city. The behavior of these OMON can be more radical than that of our [OMON] in Moscow."
March organizers vow to defy the ban and say they expect some 7,000 people to take part in the Moscow protest.
Three previous attempts to hold the march in Moscow, St. Petersburg, and Nizhny Novgorod were quashed by police.
(with material from agency reports)
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