Police have cordoned off downtown Moscow's Triumfalnaya Square shortly before two rallies are to be held at 6 p.m. Moscow time (15:00 GMT), a RIA Novosti correspondent reported Friday.
One rally, to be held by rights advocates, is sanctioned by authorities, the other, led by opposition leader Eduard Limonov, is not.
For more than a year, protesters have attempted to hold rallies on Trimfalnaya Square on the last day of every month that has 31 days to demand that the government respect Article 31 of the Russian Constitution, which guarantees freedom of assembly.
Requests to hold the rallies were invariably turned down by former Moscow mayor Yury Luzhkov, who was dismissed by President Dmitry Medvedev in September.
Current Mayor Sergei Sobyanin sanctioned October's rally, but the event was marred by an inner dispute between the protest's kingpins over the number of participants.
MOSCOW, December 31 (RIA Novosti)
