Gunmen in South Africa have killed 11 taxi drivers in an ambush, police say.

The men from Gauteng province were travelling to Johannesburg on Saturday night when their minibus was fired on.

The victims, and four others critically injured, were returning from a colleague's funeral in the coastal region of Kwa-Zulu Natal, police said.

The motive is unclear although rivalry between groups running minibus taxi routes in South Africa has led to violence in the past.

Minibus taxis are the most popular form of transportation among South Africa's population of 55 million.

Police spokesperson Brigadier Jay Naicker said the vehicle was attacked between the towns of Colenso and Weenen, in the coastal province.

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"The vehicle was ambushed. There were 11 fatalities and four were seriously injured and are in hospital," he told reporters.

"There has been a lot of taxi violence in the area but we are still investigating who the perpetrators were."