President Jacob Zuma is shocked at the deaths of 29 people in an accident involving a bus and a truck on the Moloto Road near Kwaggafontein, Mpumalanga, the presidency said on Tuesday.

"This carnage must stop. It is completely unacceptable. The fact that this particular road has gained notoriety... means there's something wrong that we need to address together," Zuma said in a statement.

"We also urge the law enforcement authorities to swiftly get to the bottom of the cause of this tragedy and the law must be firm on those found to have flouted any rules and regulations of the road, leading to such high fatalities."

Twenty-nine people were killed and 30 were injured when a bus and a truck collided on Monday night. Zuma wished the injured a speedy recovery.

"On behalf of government and all South Africans, we send our heartfelt condolences to the families of those who lost their lives in this accident. May their souls rest in peace," he said.

Transport Minister Dipuo Peters has ordered an investigation into the accident.

"The investigation team consists of the Road Traffic Management Corporation and traffic authorities in Mpumalanga," spokesman Tiyani Rikhotso said.

The team would investigate the cause of the accident and recommend ways to prevent a repeat of such an accident.