At least 18 people have been killed in a collision between a bus and a truck in northeast South Africa, according to paramedics.

Rescuers found the bus lying on its side, while the truck had come to a stop outside Machadodorp in Mpumalanga province, east of Johannesburg, the news agency ANA reported on Tuesday.

Sixteen people died at the site of the accident and two at hospital, emergency service ER24 spokesman Russel Meiring said.

The death toll had initially been given as 11.

At least 12 people were injured.

Rescuers extracted several injured people and bodies from inside and underneath the bus, Meiring told the dpa news agency.

He was unable to say how many people were on the bus and if any of those on board were unhurt.

Authorities are investigating the cause of the accident.