A Free State woman was in a coma after a Clocolan protester threw a stone in her face as she drove by, Die Volksblad newspaper reported on Tuesday.
Isabel Hugo (67) and her daughter were on their way to town when protesters surrounded the bakkie on Monday.
The report said a stone hit Hugo after it was thrown through the open window.
The woman lost consciousness and the vehicle left the road into the field next to the road.
The newspaper said Hugo was taken to a Bethlehem hospital, but she was later flown by ambulance helicopter to the Pelonomi regional hospital in Bloemfontein.
Free State health spokesperson Mondli Mvambi said Hugo had serious head injuries and was in a coma.
Protesters in Clocolan and Marquard blocked roads with stones and wire and stoned passing vehicles during the protest.
The newspaper said the protests started after the Setsoto local municipality, in Ficksburg, opened trespassing charges against residents who built illegal shacks on municipal agricultural land.
The municipality rents the land to a local farmer.
Some 80 protesters were arrested on charges of public violence by police during protests last week.