Two trucks were set alight on the R59 near Albertsdal in Gauteng – one just before midnight and the other after 01:00 on Thursday.
According to police spokesperson Lieutenant Colonel Brenda Muridili, in one incident, the driver was shot and is in a critical condition in hospital.
"Allegations are that both trucks were set alight by a group of six men driving a Hyundai H100," Muridili said. "Both trucks at the time had stopped along the R59," she added.
This is the latest in a spate of attacks on trucks.
On Wednesday morning, two trucks were set alight on the N12 highway near Daveyton in Ekurhuleni.
News24 previously reported that five trucks were set alight
Last week, nine trucks with trailers were torched in Heidelberg. On Tuesday morning, two truck drivers narrowly escaped infernos when their trucks were allegedly petrol bombed in Mpumalanga.
On Tuesday, President Cyril Ramaphosa condemned the violence and vandalism that is affecting the road freight industry.
Mary Phadi, president of the Truckers Association of South Africa, told News24 the attacks stem from unhappiness about the employment of drivers from other countries.