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.