"They closed off the road with rocks and tyres during the protest overnight," said Chief Superintendent Wayne Minnaar.
"At the moment there is ... rubble and heavy rocks blocking the intersection."
Motorists were advised to use Chris Hani, Ellias Motsoaledi and Reverend Modise roads.
Minnaar said the Rea Vaya bus lanes were also affected and the buses would use Chris Hani road.
It was not clear what the protest was about.