A bus overturned in an area of Johannesburg near South Africa's main airport early on Tuesday, killing at least 16 people, city officials said, with dozens more injured.

The bus was carrying more than 50 people to work when it crashed on a busy road near Johannesburg's OR Tambo International Airport, officials said.

The Road Traffic Management Corporation (RTMC) said the crash "has so far claimed 16 lives." Twelve died at the scene and four more in hospital.

The cause of the accident, which forced the closure of the highway leading to the airport, was not immediately known. Images from the scene showed the bus on its side.

Preliminary investigations showed that the vehicle swerved, rolled and landed facing the direction from which it came, RTMC spokesman Simon Zwane said.

Officials had earlier put the tally of people hurt at 45.

"We are lost for words. This is a disaster," Ekurhuleni city transport official Andile Mngwevu said.

A survivor of the accident told Newzroom Afrika television that the bus appeared to be speeding.

More than 11,800 lives were lost on South African roads in 2023, most of them pedestrians, according to the latest data from RTMC. (AFP)