Russia on Tuesday detained an Azerbaijani citizen suspected of stabbing to death a Muscovite in an attack that sparked some of the country's worst anti-migrant riots in years.
The suspected killer was detained just outside Moscow and sent for questioning by the Investigative Committee, the Russian equivalent of the FBI which oversees major criminal probes, a police spokesman told AFP.
Police and investigators identified the suspect as Orkhan Zeinalov, a 30-year-old native of Azerbaijan.
National television showed footage of Zeinalov being brought to Moscow by helicopter, saying he put up resistance during his detention.
Investigative Committee spokesman Vladimir Markin said Zeinalov had lived in Russia for the past 10 years and made a living driving a gypsy cab.
"It is known that he is quick-tempered and aggressive, abuses alcohol and does not have a permanent place of residence in Moscow," Markin said in a statement.
Thousands rioted in southern Moscow on Sunday over the killing several days earlier of 25-year-old local man Yegor Shcherbakov, who was stabbed to death in front of his girlfriend.
The killer fled the scene but images caught on surveillance cameras suggested he could have been from Central Asia or the Caucasus.
After a largely peaceful protest on Saturday, the rioting erupted Sunday when protesters attacked a wholesale vegetable market where they thought the suspected killer was hiding.
After the weekend riots investigators combed the place, with Markin saying the search exposed "crude violations of migration, labor and administrative legislation" at the market.
Authorities have decided to suspend trading at the market, the statement said, adding that investigators were considering opening a criminal probe against its management.
The police chief for the Western Biryulovo district where the riots took place was dismissed on Tuesday, police said, while his counterpart in Moscow's southern district which includes Biryulyovo was also fired.
Muscovites have for years chafed at the huge numbers of Muslim migrants who travel to the Russian capital in search of work.
Police routinely raid underground operations in which migrants are exploited by employers but police themselves are notorious for extorting bribes from them.
Despite a flare-up in inter-ethnic tensions, more than 100,000 Muslims gathered in Moscow to celebrate Kurban Bairam (Eid el-Adha), a major Islamic holiday known as the Festival of Sacrifice. Police reported no incidents.
'Migrants are a threat'
On Tuesday evening, around 150 people gathered for a new protest rally in southern Moscow for what nationalists described as "our answer to Kurban Bairam."
The protesters, mostly youths, walked through the neighborhood chanting nationalist slogans and smashing the windows of several cars, an AFP photographer said.
Police detained around 50 protesters, a spokesman said.
Rights activists have repeatedly warned that xenophobia is on the rise in Russia, and more and more Russians sympathise with the nationalist cause.
President Vladimir Putin, who has been accused of doing nothing to stop ultra-nationalism, has not publicly commented on the riots.
Last November, authorities allowed several thousand nationalists to march through central Moscow.
In December 2010, football fans and ultra-nationalists ran riot in the city when a demonstration against the death of a fan descended into violence.
Those protests near the Kremlin were sparked by the killing of Yegor Sviridov, a football fan who was shot in the head during a fight with men from the volatile North Caucasus.
Protesters made Hitler salutes, shouted racist slogans and attacked men of non-Slavic appearance.
The latest riots have prompted a fresh bout of soul-searching, with many media outlets blaming the trouble on authorities' inability to establish order in the Russian capital.
"On paper migrants are a workforce. In reality they are a threat," commentator Alexander Minkin wrote in a front-page article for mass-circulation daily Moskovsky Komsomolets.
"Russian residents believe they are the biggest threat."
In high-profile mayoral elections in Moscow last month, nearly all the candidates embraced anti-immigrant rhetoric.
Leading rights activists warned in an open letter at the time that society was "being drawn into such depths of visceral hatred that the only way out of it is civil war."