The South African National Defence Union (Sandu) has confirmed that the men seen on video being kicked by the police's VIP unit on the N1 highway in northern Johannesburg over the weekend are all South African National Defence Force members.

In a statement released on Tuesday night, Sandu national secretary Pikkie Greeff said they had spoken to one of the members to establish what had happened.

One of the three victims is affiliated with the union.

Greeff said the three occupants were from Johannesburg and travelling to Pretoria when a black SUV appeared next to their vehicle, while one of them was pointing a firearm at their vehicle.

"The victims' vehicle was subsequently boxed in by more SUVs and forced, in formation, to the left side of the N1 highway," he said.

"The occupants of the SUVs exited their vehicles surrounding the victims' vehicle and attempted to smash the windscreen of the victims' vehicle.

"Upon not being successful in that attempt, the assailants proceeded to smash the back window of the victims' vehicle and assault the occupants."

He said the Independent Police Investigative Directorate (IPID) had interviewed the victims on Tuesday and advised them to refrain from engaging with any South African Police Service officers while the investigation is ongoing.

He added that Sandu agreed with this approach and supported the victims.

"Sandu urges that space be given to IPID and the victims to conclude its investigation while remaining in constant contact and support of the victims while they work through this traumatic experience."

Greeff added that the union had also expressed its availability to the victims if they wanted to institute a civil action.

"Sandu again reiterates the condemnation of unlawful police brutality."

Meanwhile, a source with knowledge of the matter has told News24 that four warrant officers from the police's Presidential Protection Services (PPS) were handed notices of suspension on Tuesday.

Two more police officers involved in the incident, where the two men were dragged from their vehicle and assaulted, also face suspension.

A video of the incident showed one man lying motionless on the asphalt while his assailants were kicking him. The other is sitting, his arms protecting his face from the kicks also coming his way.

The officers then return to their black BMWs and take off, leaving the men on the ground. One slowly gets up while the other lies motionless, the video showed. 

News24 has since established that the officers were part of Deputy President Paul Mashatile's security detail, and that the convoy was said to have been driving Mashatile home. 

The source told News24 that the officers claimed that the driver of the vehicle had tagged Mashatile's convoy for a long while before it was pushed off the road. 

The officers further claimed that the motorist had tried to get close to Mashatile's vehicle, prompting them to act.