Four trucks were burnt in Mpumalanga on Wednesday morning while two others caught fire in separate accidents in the Free State and Gauteng.

Mpumalanga police spokesperson Brigadier Selvy Mohlala said the four trucks were burnt on Wednesday morning at around 05:30 on the N2 between Piet Retief and Ermelo.

The drivers were reportedly ordered, at gunpoint, to exit the trucks before they were torched, said Mohlala.

"It is alleged that people emerged from the grasses and approached the trucks with firearms and instructed the drivers to get out otherwise they would burn them inside. They [drivers] then left and ran away."

One person, a passenger, sustained burn wounds on her face and feet. It is understood that she was sleeping inside one of the trucks when it was set alight. She has since been taken to hospital for treatment.

No arrests have been made yet and the motive for the attack is still unclear.

The number of trucks that have been destroyed by arson in the past few days in KwaZulu-Natal, Limpopo and Mpumalanga has risen to 20.

In a separate incident on Tuesday night, a tanker carrying paraffin overturned on the N1 highway in Bloemfontein after the driver lost control of the vehicle while going around a bend, said Road Traffic Management Corporation spokesperson Simon Zwane.

The driver and passenger escaped with minor injuries.

In a second incident, in Gauteng, a truck caught alight after its tyre burst while it was travelling on the R59 in Meyerton.

Ekurhuleni Metropolitan Municipality Police Department spokesperson Kelebogile Thepa said the truck was pulling two trailers when the tyre on one of the trailers burst and caused the trailer to catch fire.

The quick-thinking driver unhooked the trailers to prevent the truck from catching alight, said Thepa.

No one was injured in the incident.

Thepa said the incident had not been linked to the series of truck torchings around the country.

News24 previously reported that the number of trucks that had been destroyed in arson attacks over the three days until Monday was 16, after five trucks were set alight in KwaZulu-Natal and Limpopo.

Eleven were torched over the weekend – six in KwaZulu-Natal on Saturday and five in Mpumalanga on Sunday night.