The buses were en route to Johannesburg from the Eastern Cape when they came under fire.
Translux and City to City buses are owned by holding company Autopax, which is a wholly owned subsidiary of the Passenger Rail Agency of South Africa (Prasa).
Prasa spokesperson Nana Zenani said the buses had been carrying 36 and 56 passengers respectively.
“According to witnesses, a white vehicle overtook the buses and the occupants of the vehicle fired shots at the two buses,” said Zenani.
Police spokesperson Lieutenant-Colonel Thulani Zwane said a 42-year-old bus driver who was shot twice had been killed. Zwane said the second bus driver, aged 40, sustained two gunshot wounds and was taken to hospital.
No passengers were injured.
The SA Transport and Allied Workers Union (Satawu) called for swift action from the authorities.
Satawu spokesperson Zanele Sabela said the 42-year-old driver had died immediately and his bus came to a stop after it hit a barrier. Sabela said the second driver was able to control the vehicle despite being shot and engaged the handbrake before he collapsed.
Zenani said services from Johannesburg had been suspended.
Prasa group chief executive Dr Nkosinathi Sishi sent condolences to the family of the bus driver who was killed.
“Prasa is shocked at the apparent lawlessness and cruelty of this attack. Our drivers and passengers are our priority” said Sishi. “We would like to assure our commuters and drivers that we are working with the authorities to get to the bottom of this unfortunate attack.”
According to Sabela, workers at the state-owned company had stopped working because they were concerned for their safety.
“They are calling for the ministers of transport and police to come and address them,” she said.
The union said buses belonging to Eagle Liner and African People Mover had been targeted at the same spot on the R56 in July. “Thankfully, the drivers were not shot at, but all the bus windows were smashed.
“The two companies have since changed routes,” said Sabela.
“We have all seen the devastation caused in the trucking industry and across Gauteng communities in recent weeks. We call on all aggrieved transport stakeholders to come out from the shadows and express their concerns in a responsible manner so that they can be addressed,” said Sabela.
Kwanele Ncalane, the KZN spokesperson for the Department of Transport and Community Safety, said the department would conduct a speedy investigation.
“At this stage, we take this as a pure act of criminality, however we await the police to confirm the actual cause of the shooting,” he said.
Ncalane said the department had not established if the shooting incidents were linked to the truck attacks.
“The department will engage the company. Should there be any issues, we will move with speed in finding solutions and engaging all affected parties,” he said.
The police said cases of murder and attempted murder had been opened at Ixopo police station for investigation.