The victims were in a minibus travelling to Johannesburg when the massacre happened on Saturday night.
They were returning from a colleague's funeral in the western coastal region of Kwa-Zulu Natal, the BBC reports. Four men managed to survive but remain critically injured in hospital.
All 15 were members of the Gauteng taxi association.
The attack occurred between the towns of Colenso and Weenen.
Although the motive remains unclear, tensions between different taxi groups vying for the same routes have regularly spilled into bloodshed in the country's major cities.
Police spokesperson Brigadier Jay Naicker said investigations were ongoing. “The vehicle was ambushed," he said. "There were 11 fatalities and four were seriously injured and are in hospital. There has been a lot of taxi violence in the area but we are still investigating who the perpetrators were."
In a single deadly weekend in May some 10 drivers were murdered in Cape Town due to rivalries. Just last week two more were killed in Johannesburg while travelling with a police escort.
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