Russian police rounded up more than 1,600 migrants on Monday in Moscow after rioting swept through a southern neighborhood a day earlier over a fatal stabbing of a Russian that many residents blame on a man from the Caucasus.
An advocacy group warned migrants from the mainly Muslim Caucasus and Central Asia of an increased risk of attacks after the worst ethnic disturbance in Moscow in three years.
Some 1,200 people were detained at a wholesale vegetable market that was stormed on Sunday night by rioters after a protest over the stabbing death of an ethnic Russian man, police spokesman Alexei Shapkin said.
Another 450 were detained in northeastern Moscow, also near a vegetables market employing migrant workers.
Police said they were all detained to check whether they were involved in any wrongdoing, but they have not been accused of any specific crime. Footage showed detainees standing against walls or lined up in front of camouflage-clad police.
By rounding up migrants, authorities seemed to be trying to appease residents who had rallied in the Biryulyovo district to demand police find the killer of Yegor Shcherbakov, 25, and take more action to prevent crimes by migrants.
Migrant labor has played a significant role in Russia's transformation during an oil-fuelled economic boom that took off around the time President Vladimir Putin came to power in 2000.
But many in Moscow are uneasy at the influx of migrants from Russia's heavily Muslim North Caucasus and ex-Soviet states of the Caucasus and Central Asia, although many do low-paying jobs, such as in construction, that few local residents want.
On Sunday, the mob in the southern neighborhood fought with police, smashed shops and vending stalls and stormed the vegetable market, targeting sites employing migrant workers.
Police arrested at least 380 people as they struggled to quell the violence, which injured several police and others and shone a spotlight on persistent tension between ethnic Russians and people from the Caucasus and Central Asia.
Russian authorities frequently carry out raids detaining illegal immigrants but critics say such efforts are undermined by corruption in law enforcement agencies.
"We must learn to live together ... and counteract rampant corruption and related attempts to break up our country by exploiting ethnic problems," Russia's human rights ombudsman, Vladimir Lukin, told state TV.
A group that lobbies for labor migrants in Russia warned of an increased risk of ethnic violence in Moscow on Monday.
"The nationalists are pursuing their political goals. This is clearly very dangerous. We are warning migrants to be careful for now in crowded areas and on public transportation," said Mukhamad Amin, head of the Federation of Migrants of Russia.
The rioting came before Eid al-Adha, an Islamic holiday that most Russian Muslims begin celebrating on Tuesday. In Moscow, ethnic tension is often higher during such holidays because large numbers of Muslims gather at the city's few mosques.
Putin has frequently warned of the dangers of ethnic and religious violence in multicultural Russia, which is mostly Slavic and Orthodox Christian but has a large Muslim minority.
Putin said this month Russia needed migrant laborers in industries such as construction but, in a nod to anti-migrant sentiment, suggested their numbers could be restricted in trade.
He also suggested the Kremlin would resist calls to establish visa regimes with several former Soviet republics, indicating this would undermine reintegration efforts that he has made a priority in a third presidential term.