South African protesters clashed with foreign nationals on Thursday as tensions over migration were reignited by a court order that government must restart processing asylum applications.
Violence erupted in Johannesburg's Soweto and the east coast port city of Durban, with several cars torched and small foreign-run stores looted.
It followed fresh protests called by movements targeting undocumented migrants that were behind demonstrations earlier this year that led tens of thousands to leave the country.
In Durban, allegations that a foreign national assaulted a South African demonstrator sparked violence that led to the burning of at least 14 vehicles, police said.
Three foreign nationals were arrested, they said.
Police opened fire with rubber bullets to disperse protesters who reportedly set alight a business run by foreigners and looted others, AFP reporters said.
A municipal building was also set on fire, an official said.
In Soweto, at least 10 vehicles were torched but there were no reports of injuries, police said.
Looters raided small convenience stores, which are often run by migrants and are a particular target of bouts of xenophobic unrest in South Africa.
Police were pursuing "those who are responsible for the chaos", police acting national commissioner Lieutenant General Puleng Dimpane told reporters.
"The right to raise concerns and to protest does not give anyone the right to commit crime," she said.
The court ruling behind the flare-up of xenophobic tensions said certain provisions of a government act on refugees were unconstitutional.
This, the court said, was because the provisions prevented some individuals from accessing the asylum system on procedural grounds, including if they entered the country irregularly.
The ruling led hundreds of people to flock to government refugee centres in recent days, reportedly including people who do not qualify for asylum claims based on persecution or other dangers in their home countries.
Warning against disinformation, the government stressed on Wednesday the judgement "does not grant refugee status or permanent residence automatically to anyone who enters South Africa".
It was "concerned about certain unintended consequences" of the ruling, a statement said, reiterating commitment to measures announced in June to manage migration.
These include boosting control of the borders, cracking down on human smuggling and accelerating deportations of people who do not qualify to remain.
The continent's wealthiest nation has long been a magnet for migrants from elsewhere on the continent who are seeking employment.
It has experienced periodic outbreaks of xenophobic violence for nearly two decades, sometimes based on disputed claims that foreign nationals take scarce jobs and resources from locals.
Complaints about illegal immigration have grown ahead of local government elections on November 4, with unemployment above 30 percent another key issue.
Weeks of protests by populist, anti-immigrant groups demanding undocumented migrants leave by June 30 led tens of thousands to flee, some repatriated by their governments, straining South Africa's ties with other countries on the continent.
At least four foreign nationals were killed in that violence, according to the South African police, though some foreign governments said the toll was higher.
The largest numbers to leave were from Zimbabwe and Malawi but thousands more were from countries including Ghana, Kenya, Lesotho, Mozambique, Nigeria and Uganda.
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