At least 800 people were arrested in central Moscow on Wednesday evening as police held a massive operation to prevent new race-hate riots.
Police also said that 30 people were injured as officers sealed off areas of the city around the Kievsky train station.
Many of those detained were in possession of knives and stun guns.
Reports had earlier said that nationalists and migrants from Russia's North Caucasus were planning to clash.
Police eventually managed to disperse a crowd of around 1,500 that gathered at Europa Square, although groups of youths chanting nationalist slogans tried to close off a nearby street.
The developments came after the Russian capital saw its biggest public disturbances for almost a decade on Saturday as a 5,000-strong crowd of nationalists and football hooligans clashed with police near Red Square. Rioters also attacked people from the country's North Caucasus region.
President Dmitry Medvedev called the disorder, which was triggered by the death of a football fan in a brawl with North Caucasus migrants, a threat to the very stability of the Russian state.
There were also arrests in St Petersburg as police prevented clashes between nationalists and Caucasus migrants.
MOSCOW, December 15 (RIA Novosti)
