Marauding war parties killed at least 29 people over a 24-hour period in black townships, police said, as an initially peaceful May Day turned to horror after sunset.

Escalating vendetta shootings, knifings and spearings by supporters of rival black political factions have killed nearly 100 people since Saturday.African National Congress Deputy President Nelson Mandela has called for urgent intervention by the authorities to stop the violence, and the ANC has threatened to break off dialogue with the government unless it acts to end the slaughter.