Signs of social instability could harm South Africa's image and investor sentiment, undoing gains achieved by hosting the successful soccer World Cup tournament that ended on Sunday.
Police said they had arrested seven people and flare-ups in the Western Cape in the Cape Town area, were matters of concern but no one had been injured so far.
"There were two shacks that were burned in separate areas and there's been sporadic incidents of looting and threats have been made on foreign nationals," said Western Cape police spokesman Frederick van Wyk.
"Police have responded. At this moment there is a heavy police contingent, which also includes Metro Police and SANDF (South African National Defense Force)."
Scores of migrants from neighboring African states took refuge at police stations in the Western Cape on Sunday night, fearing for their lives and worried after shops run by migrants had been looted, national news agency SAPA reported.
Sixteen years since the end of white minority rule, poor blacks are frustrated that their social conditions have not improved and the ruling African National Congress's promises of better housing, education and healthcare have not materialized.
South Africa has attracted millions of workers from across the continent and further afield where they compete with locals for scarce jobs and resources. Two years ago more than 60 people were killed during anti-foreigner attacks.
Just a day after the World Cup ended, about 300 residents in Lenasia, south of Johannesburg obstructed traffic with burning tires and broken toilet seats to protest about living conditions.
"Police have been deployed to the area and are trying to clear the crowds," said Wayne Minaar of the Johannesburg Metro Police Services.
Such protests, which were common before the World Cup, had died down during the 32-day soccer tournament.
