Nine others were wounded and taken to hospital.
This latest mass shooting has left the Jumpers informal settlement in shock and has once again raised concerns about gun violence in the province.
Police said a group of about ten armed men arrived in a Toyota Quantum near a petrol station in Cleveland before splitting up and entering the settlement through different entrances.
The suspects then opened fire at multiple locations, killing twelve people and injuring nine others.
Gauteng police spokesperson Dimakatso Nevuhulwi said the gunmen fled in the same vehicle that dropped them off.
Police have launched a manhunt for the suspects, while investigators work to establish a motive for the attack.
This is a developing story.
Nkosikhona Malinga-Mnisi
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