Metrobus said the illegal strike by bus drives continued on Monday and services had been suspended.
Metrobus Corporate Services GM Ranti Mahlabana said: "It does appear that this is a continuation of an illegal strike that started on Friday afternoon".
At least 200 Metrobus routes have been shut down due to the strike.
Mahlabana said: "Metrobus Management sincerely apologised to all their commuters who would be affected by this illegal strike this morning. We will make all efforts to try an ensure that the services are returned to normality as a matter of urgency.
"We therefore appeal to our commuters to make alternative arrangements for transport to their various destinations."