South Africa's police watchdog agency is investigating the death of a man who had been tied to the back of a police van and dragged while a bystander filmed.

Moses Dlamini of the Independent Police Investigative Directorate said Thursday on eNCA, a South African news channel, that he is "shocked" by the police conduct and that a murder probe is underway. The cause of death was not immediately clear.

The Daily Sun, a South African newspaper, published video footage in which uniformed police subdue the man. They tie him to the back of a police vehicle in front of a crowd. The event was apparently filmed on a cellular telephone.

South African media say the man was a taxi driver who had been approached by police east of Johannesburg.