Lieutenant Colonel Dlamini said police were investigating the incidents that happened on Friday and have not linked them.
He said the two incidents have not been linked because police do not believed that they were carried out by the same people.
Gunmen opened fire on a Rea Vaya bus wounding four people in Orlando West and left one of them in a critical condition.
In the second incident a driver and four passengers were injured when a bus was shot at in Moletsane.
The Rea Vaya bus rapid transit (BRT) system which aimed to break the monopoly of minibus taxis on public roads, was introduced in August last year.
The BRT buses transport commuters between Soweto and central Johannesburg, quicker at a cheaper fare than that paid to taxis.
Some taxi associations have been against the implementation of the rapid bus system, arguing that the system would put them out of business.