About 1,400 sub-Saharan Africans, mainly West Africans, have been taken from their homes in Algiers by riot police since Thursday, according to the Algerian League for the Defence of Human Rights (ALDHR) .
Pregnant women and children are among the migrants.
The ALDHR says some have been injured and others have been taken to a holding centre just outside Algiers.
The Algerian authorities warned in late September that they intended to expel tens of thousands of sub-Saharan migrants.
There have recently been clashes between migrants and locals in southern Algeria - the result of what seemed to be pressure for jobs.