Police clash with football fans and right wing protesters during a rally in central Moscow December 11, 2010. [Photo/Agencies]

The weekend rally began as a protest against the killing of a member of the Spartak Moscow soccer team's fan club, who was shot with rubber bullets during clashes with Caucasus natives at a bus stop earlier this month. Spartak fans claimed corrupt policemen detained one suspected killer following the fight, but released others because they had powerful backers in the Caucasus.

Moscow police chief Vladimir Kolokoltsev acknowledged Monday that investigators had made a mistake and said three more suspects have been arrested.

Russian media have been abuzz with rumors that some people from the Caucasus could try to take revenge for Saturday's riots, even as community leaders described the allegations as a provocation and called for calm.

Anxieties about what would happen Wednesday were palpable hours before protesters starting gathering. A shopping mall just outside the train station shut down hours ahead of schedule, and most stands at a nearby flower market - operated mostly by people from the Caucasus - were closed. Authorities towed cars in anticipation of possible clashes and helmeted police were on standby on a square and around the mall early in the morning.

A video in which anti-Caucasus slogans were interlaced with footage of ethnic minorities from southern Russia beating up policemen and Slavic men was posted on the website of the Spartak fan club Wednesday.

"They don't respect our traditions," the slogans said in reference to the Caucasus natives. "Now is the time to show them who's in charge. They went too far."

On Monday, President Dmitry Medvedev urged police not to hesitate to use force to put down riots, saying that leaving hate crimes unpunished would jeopardize stability.

Hate attacks in Russia peaked in 2008, when 115 people were killed and nearly 500 wounded, according to Sova, an independent watchdog.

Some Russia experts noted links between nationalist groups and some part of officialdom. Opposition groups claim that pro-Kremlin youth organizations have hired soccer fans and racists to carry out attacks on Kremlin critics.