Moscow police arrested more than 380 people Sunday during a race riot in which nationalists outraged by a murder blamed on a migrant smashed shop windows and assaulted security guards, AFP reports.
The crowd chanted "Russia for Russians!" and other neo-Nazi slogans during a protest that swelled to more than 1,000 people in an industrial district of southern Moscow and prompted police to order a city-wide security alert.
Witnesses reported police helicopters circling over the southern Biryulyovo district in scenes reminiscent of a war zone and not witnessed in Moscow since President Vladimir Putin returned to power for a third term in May 2012.
"I cannot believe this is happening in our city," one middle-aged woman told Russian state television.
"I am afraid to let my children out on the street," said another woman.
A Moscow police spokesman told Russian media that the city's entire active security force had been mobilised several hours into the riot.
"Five police officers were injured while making arrests," the RIA Novosti news agency quoted a police spokesman as saying.
"Four of them were treated at the scene and another one -- a commander of an OMON (riot police) battalion -- sustained serious injuries."
Police said they had cut off all traffic in the Biryulyovo district and shut down a major highway as a precaution.
The riot broke out in the afternoon when an organised group of several hundred youths dressed predominantly in black jumped out of a street underpass and attacked a vegetable market where they though the suspected killer was hiding.
They were outraged over the murder on Thursday of a 25-year-old local man named Yegor Shcherbakov. Police said he was stabbed by an unknown assailant in unclear circumstances while his fiancee -- identified only by her first name Ksenya -- watched.
The killer fled the scene but was caught on surveillance cameras that suggested he could have been from Central Asia or the Caucasus.
"I know they will find the killer," Ksenya told Russian state television.
The incident prompted an emergency Moscow security meeting and promises of urgent action from the city's most senior police officials.
"Every measure will be taken to stop the criminal," district police chief Alexandre Polovinko said at the scene of the protest.
"The best investigators have been assigned to the case."
Witnesses said the protesters threw empty beer bottles at shop windows and hurled clubs and even hammers at a riot police force that rushed to the scene in about a dozen buses.
Security officials said they had arrested about 380 people in Biryulyovo and 60 others in a separate protest in northeastern Moscow that appeared to be unrelated and sparked by still unclear circumstances.
Ethnic tensions have simmered for years in Moscow and other major Russian that have been flooded by migrant labourers from predominantly Muslim regions of the Caucasus and Central Asia.
Sunday's riot was the largest since 5,000 football fans and nationalists protested on Moscow's central Manezh Square in December 2010 over the killing by a man from the Caucasus of an ethnic Russian supporter of a local club.
Putin surprised many observers at the time by attending the funeral of the slain Moscow football supporter despite the presence at the ceremony of some of the city's most ardent nationalists.
Ways to stem the migration of ethnic Muslim labourers to big Russian cities was also a major theme of last month's Moscow mayoral elections won by Putin ally Sergei Sobyanin.
Southern migrants frequently endure poor labour and living conditions and are increasingly regarded with disdain by many Muscovites.
Veteran nationalist lawmaker Vladimir Zhirinovsky told Russian state television that the latest murder in Moscow meant it was time for the authorities to crack down on migrants.
"Moscow is overflowing with migrants," Zhirinovsky separately wrote on his Twitter account.
"We need a three-year programme that, once completed, will rid us of this foreign work force."