A 12-year-old girl and a toddler were killed when their family was attacked in their home in Butterworth, Eastern Cape police said on Wednesday.
"It is alleged that four family members were attacked by an unknown suspect or suspects, between Monday night and Tuesday morning while asleep," Lt-Col Sibongile Soci said.
All four had serious head injuries. The 12-year-old daughter died on the scene and her one-year-old brother died later in hospital.
The attackers fled the scene and no arrests had been made by Wednesday morning.
Soci said nothing was stolen from the family's home and the motive for the attack was still under investigation.
Last Wednesday, a 66-year-old woman and a baby were found strangled in their home in Delmas, Mpumalanga.
The day mother's body was found under a carpet in an outside room. The baby was found under a bed in the main house. The motive was also not known.