Police Captain Andre Beetge says the incident happened on the Addo Road at around 7pm.
"According to the couple, 46-year-old Jochen Gass and 50-year-old Anja Engelmann, they were forced to stop when they drove up to a burning tyres barricade," Beetge said.
"When they attempted to turn the car around, their vehicle was pelted with stones by protestors."
Beetge said only Gass was slightly injured by a stone that hit him on the right side of the neck.