Hundreds of foreigners living in South Africa took refuge in police stations and churches as week-old violence against them spread further across poor townships, local media reported on Sunday.
Numbers of casualties since the attacks against Zimbabweans and other immigrants began a week ago varied, with some reports on Sunday putting the death toll at around 10.
Some South Africans, especially those living in poor areas of high unemployment, accuse Zimbabweans and other newcomers of fuelling the high crime rate and taking scarce jobs.
The attacks have renewed the authorities' fears that xenophobia is on the rise in a country which was once known as one of the most welcoming to immigrants and asylum seekers, especially from Africa.
Local radio said angry mobs had at first attacked houses owned by immigrants from neighbouring Zimbabwe, Mozambique and other countries in Alexandra township.
But now these attacks had spread to other settlements and Johannesburg's city centre. Properties had been looted and destroyed.
"There have been some incidents in the Alexandra area where police opened fire using rubber bullets to disperse crowds," police spokesman Govindsamy Mariemuthoo said on local radio.
"There've been problems also in the East Rand. In the Boksburg area some shacks have been set alight," he added.
Mariemuthoo was not reachable for further comment.
The anti-foreigner violence has rattled authorities and the business community, and President Thabo Mbeki urged police to move quickly to find the instigators.
"It's necessary to move as quickly as possible to establish all the causes and the players in all of this, so that we can then deal with the matter more effectively," he said on national broadcaster SABC radio.
"The communities ... should act together with the police and together we should say this is very, very wrong. It is unacceptable that there should be this kind of violence."
Medical rights group Medecins Sans Frontieres said the situation now amounted to a humanitarian crisis.
"I have been to many refugee camps and situations and this definitely is along those lines," spokesman Eric Goemaere told SAPA news agency. "This reminds me of a refugee situation. I have treated bullet wounds, beaten people, rape victims and the people are terrified."
The violence has also affected businesses owned by immigrants from Asian countries like Pakistan.
An estimated 3 million Zimbabweans have fled to South Africa as a result of the political and economic crisis at home.
