At least 12 people were killed, and nine were injured on Tuesday evening when gunmen opened fire at an informal settlement in Cleveland, east of Johannesburg, police said on Wednesday.South Africa has one of the world's highest murder rates, averaging about 60 a day. (Representational)Police said in a statement that they had launched a manhunt for more than 10 suspects following the attack at the Jumpers informal settlement, Reuters reported. Informal settlements in South Africa are unplanned residential areas usually made up of shacks or similar structures.The motive for the attack is not known yet, and an investigation has been launched.Police officials quoted by Reuters said that the suspects arrived in a white Toyota Quantum, entered the settlement from two access points and opened fire at multiple locations before fleeing in the same vehicle.According to Sky News, officers found several people with multiple gunshot wounds at the scene. Eight men and three women were declared dead there, with another man later succumbing to his injuries in the hospital.The nine wounded victims were also taken in for medical treatment.South Africa has one of the world's highest murder rates, averaging about 60 a day.