• Unemployment, widespread poverty and income disparities have been blamed.
Police arrested dozens of people in South Africa's commercial capital Johannesburg on Monday after rioters looted shops, burned tyres and blocked road junctions - the second outbreak of urban rioting in a week.
Police were unable to say what had triggered the violence, although unemployment at close to 30%, widespread poverty and income disparities have all been blamed for recent disturbances and attacks on immigrants.
Last week, hundreds of protesters in the administrative capital Pretoria set fire to buildings, looted mostly foreign-owned businesses and clashed with police, who fired rubber bullets at the crowds.
"We've stabilised the situation and arrested a few dozen people already," Johannesburg police spokesman Wayne Minaar said.
"We can't confirm the final figure right now but they will be charged for public violence ... There's also a charge of attempted murder being investigated."
He could not confirm media reports that police had fired rubber bullets at the rioters, or say whether most of the businesses that had been attacked were foreign-owned.
In 2015, at least seven people were killed in a spasm of attacks on immigrants.