A man with a mental illness was allegedly beaten to death by Red Ant Security Services in Midvaal, south of Johannesburg on Thursday, Gauteng police said.
The man's body was found on the R59 highway during a service delivery protest, police spokesperson Kay Makhubela told News24 on Friday.
A case of murder has been opened. No arrests have been made, he said.
Red Ant Security Services on Friday said it would provide comment on the matter later in the day.
Makhubela said the highway remains closed and police are monitoring the situation.
Mayor Bongani Baloyi told News24 that there were growing frustrations over land issues in the area.
He said that during the protest an altercation between the Red Ants and the community ensued, with residents throwing stones.
The security service officials were trying to prevent residents from blocking the roads with stones and burning tyres, Baloyi said.
Last Friday, two people were killed during a clash over land in Lenasia, south of Johannesburg.
Makhubela said at the time that Red Ant workers were evicting dwellers along the freeway there.
- Additional reporting by Caryn Dolley