Moscow police rounded up and arrested more than a thousand migrant workers at a vegetable warehouse on Monday morning, hours after hundreds of ultranationalists clashed with riot police. The rioters had overturned cars and raided a shopping centre used by migrants after the murder of an ethnic Russian was blamed on a man from the Caucasus.

Police arrested more than 1,200 people in what was called a "pre-emptive raid" on the warehouse where the rioters believed the killer worked, Russian news agencies reported.

Sunday's rioting in the southern Biryulyovo district of Moscow, which escalated after hundreds gathered where Egor Shcherbakov, 25, was murdered last week, marked the capital's worst nationalist unrest in three years.

Nationalist mobs chanted "Russia for Russians"and images from the scene show a car flipped on to its roof scattered in watermelons.

About 380 of the ultranationalists were arrested on Sunday night, although most were released. Seventy face administrative proceedings, while two are likely to face criminal charges. The police have opened a criminal investigation into "hooliganism".

Nationalists in masks hurled bottles at police, dressed in helmets and urban camouflage, who fought back with batons. Six riot police officers were wounded; two were taken to hospital.

The violence prompted the interior ministry on Sunday to activate Vulkan-5, an emergency security regime that deploys the entire Moscow police force and that was last activated after the Moscow metro bombings killed 40 people three years ago.

Late on Sunday night the police had the situation under control, although migrant communities remained tense. The head of the Federation of Migrants on Sunday warned migrants to remain at home for fear of random attacks across the city.

Police have said Shcherbakov was stabbed in front of his girlfriend on 10 October. The following day a photograph of an alleged suspect, who appeared to be from the Caucasus region, was circulating on nationalist websites.

In December 2010, violence erupted in the capital when thousands of ultranationalists massed outside the walls of the Kremlin after an ethnic Russian football fan was killed by a man from the North Caucasus.

Animosity towards immigration has grown rapidly in the last 10 years as the inflow of migrants from central Asia and Russia's north Caucasus region has boomed.