Eight South African policemen have been arrested on suspicion of murder after dragging a man tied to the back of a police truck through a busy Johannesburg street in an incident broadcast around the world.

Footage showing the treatment of the Mozambican taxi driver has further damaged the reputation of the police force in South Africa, where more than 1200 people a year die in police custody.

"They will answer to a charge of murder when they appear in court on Monday," said Moses Dlamini, spokesman for police watchdog the Independent Police Investigative Directorate (IPID).

Mido Macia, 27, was found dead in detention with signs of head injuries and internal bleeding, according to an initial post-mortem report released by the IPID.

The video shows Mr Macia scuffling with police, who subdue him. He is then bound to the back of a pick-up truck by his arms before the vehicle is driven off in front of scores of witnesses in the east Johannesburg area of Daveyton.

"We would like to assure the country and the world that what is in the video is not how the South African Police Service in a democratic South Africa goes about its work," Commissioner Riah Phiyega told a news conference.

Before the arrests, she said the eight officers had been suspended and the station commander would be removed from his duties.

President Jacob Zuma and opposition politicians have condemned the incident. "The visuals of the incident are horrific, disturbing and unacceptable. No human being should be treated in that manner", Mr Zuma said.

Police told media they had detained Mr Macia after he parked illegally, creating a traffic jam. They said he had then resisted arrest.