Police used rubber bullets to break up looters in Alexandra township north of Johannesburg, authorities have said. Mobs have attacked migrant-owned shops in various areas around the city.
Wave of anti-immigrant attacks, which has so far left six people dead, caused fresh violence around the South African capital of Johannesburg early Saturday.
Small groups of rioters targeted shops in other areas around the city, police said.
Police were out in force in the impoverished township of Alexandra, according to media reports, after looters built barricades and burned tires during the night. Security forces had to fire rubber bullets in order to disperse the rioters, police spokesman Lungelo Dlamini told AFP news agency.
"More than 30 people were arrested last night. At this stage the situation is calm but we plan to increase our deployment," he said.
"They are going to be charged for public violence, malicious damage to property, house breaking and theft," he said.
Cars and shops belonging to immigrants were torched in central Johannesburg during recent days.
Outrage among neighbors
The xenophobic attacks started in the eastern coastal city of Durban several weeks ago, after the Zulu king Goodwill Zwelithini was reported to have said that foreigners must "take their bags and go."
The king later dismissed the claims and urged the population to be calm, saying that he had only referred to foreign nationals who were committing crimes. However, the wave of violence continued to spread, claiming six lives in Durban and forcing thousands of migrants to take refuge in makeshift camps.
The riots have also sparked international outrage with Zimbabwe, Malawi and Mozambique announcing plans to evacuate their citizens. UN refugee agency UNHCR also criticized the attacks, saying it was "extremely concerned."
The resentment in the countries neighboring South Africa is additionally aggravated by the fact that they took in thousands of exiles from South Africa during the apartheid era.
String of attacks
South Africa has a population of roughly 52 million people, with some 5 million immigrants, mostly from other parts of Africa, living in the country. Despite a relatively successful economy, the country is burdened by high unemployment and some immigration critics contend that the foreign workers are taking jobs and opportunities away.
Several foreigners have been killed in the township of Soweto, south of Johannesburg, in a separate wave of attacks in January. Roughly 60 people died in similar unrest in 2008.
dj/kms (AP, AFP)