Foreign-owned shops in the Jeppestown area of Johannesburg were attacked overnight, the police said as they called for calm over fears that the attacks could trigger widespread unrest fuelled by the country's economic troubles.
In the past two weeks, shops and homes owned by Somalis, Ethiopians, Malawians and other immigrants in Durban and surrounding townships have been targeted, forcing families to flee to camps protected by armed guards.
About 4,000 people marched through Durban, chanting "Down with xenophobia!" and "A United Africa" at an event attended by residents, students and local religious and political leaders.
"There are tensions in various parts of the country between some locals and foreign nationals (but) lawlessness will not be tolerated," National Police Commissioner General Riah Phiyega said in a statement.
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"Overnight, there was a flare-up of violent attacks and looting in Jeppestown, Johannesburg," she added.
"Six male suspects have been arrested for public violence and housebreaking. The suspects allegedly broke into foreigners' shops."
Police, who also reported tensions in Pietermaritzburg city, called for community leaders to help reduce tensions and added that false rumours of attacks were increasing fear.
South Africa's economic growth was just 1.5 per cent last year and unemployment is at around 25 per cent -- soaring to over 50 per cent among the young.
Violence against immigrants in South Africa is common, with unemployed locals accusing foreigners of taking their jobs.
In 2008, 62 people were killed in similar violence in Johannesburg townships.