Four people were killed and shops owned by immigrants in South African townships in the coastal city of Durban looted and burnt, police said on Monday, as violence between residents and foreign nationals escalated.
Those killed include an Ethiopian, whose shop was petrol bombed last week, an African immigrant whose nationality was not immediately known and two South Africans, police spokesman Thulani Zwane said.
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Hundreds of people fled their homes after the violence broke out two weeks ago, while police said 28 people have been arrested for looting and torching immigrants' shops.
"We received reports that some of the shops belonging to foreign nationals were looted and some of them were burnt down overnight," Zwane said.
South Africa, with a population of about 50 million, is home to an estimated 5 million immigrants.
Some politicians and residents say some of the immigrants are in the country illegally and accused them of committing crimes and taking over local shops and jobs.
Some foreign nationals say they are legally in the country, running businesses to provide services for the residents.
South Africa's unemployment stood at 24 percent in the fourth quarter of 2014, according to government data.
President Jacob Zuma on Sunday called for an end to the violence and directed the police and the home affairs ministers to work with local officials to stop the violence and enforce laws to curb the growth of illegal trading and unlicensed shops.
"We reiterate that there can be no justification for attacking foreign nationals," Zuma said in a statement.
"Those who are in the country illegally should be reported to the police and they will be returned to their countries of origin in a lawful manner."
In 2008, more than 60 foreigners were killed in violence that analysts believe had its roots in tensions over a lack of jobs. South African unemployment is around 25 percent and youth joblessness is nearer to 40 percent.