South Africa has been rocked by scenes of hatred and savagery as poor township blacks turn on the migrants they claim have taken their jobs.

More than 20 have been killed and thousands forced to flee by gangs wielding guns, clubs and machetes.

Most horrifying of all, for a country which thought the worst was behind it, has been the return of necklacing, the appalling method of killing which involves putting a petrol-filled tyre around a victim's neck and setting it ablaze.

Savagery: Police try to save a man who was set on fire by a mob attacking immigrants in Reiger Park, near Johannesburg

In the violent 1980s and 1990s, necklacing was a common sentence imposed by 'people's courts' on collaborators with the apartheid regime and criminals.It was frequently carried out in the name of the now-ruling African National Congress and was alleged to have been endorsed by Nelson Mandela's then wife, Winnie.