Some 6,000 people have fled a wave of attacks on foreigners in South Africa, which has left at least 22 dead, aid workers say.
"This is a classic refugee situation," Rachel Cohen from Medecins Sans Frontieres (MSF) told the BBC.
Many of those who have sought refuge in police stations, churches and community halls are Zimbabweans, who have fled violence and poverty at home.
Up to three million Zimbabweans are thought to be in South Africa.
The BBC's Caroline Hawley in Johannesburg says the immigrants have become a scapegoat for social problems, such as unemployment, crime and a lack of housing.
JOHANNESBURG BLADEThey arrived that morning, in their ragged and born souls,
Slipping through the tall grassland like murmuring insects;
Fearless, save for that which remained hidden, voiceless,
The glowering grumble of an unconvinced horror,
Clanging sabers, improvised tools, a honed blade
To tap between the fleeing bone and the undead.
From this drab symphony arose an ancient isle’s composition
Clanging steel hastily moving inland among the murmuring tone
Of fleeing edges desperation. The thing being chased was nearing
With each footstep, with every marauding and rumpled lust,
It closed in on the whispering blades and raging hearts,
Near enough that they tapped into their own flesh.
© 2008 mrp/tpm