JOHANNESBURG (AFP) - A South African teenager will appear in court on Monday for allegedly hacking to death four family members with an axe, including his mother and an infant sister.

The Benoni Magistrates court will hear the case after the 14-year-old spent the weekend in custody over the grisly murder of his mother, grandmother, brother and baby sister.

Two sisters, aged eight and nine, escaped to the neighbours during the killings and raised the alarm early on Friday morning in the Etwatwa informal settlement east of Johannesburg.

Police tracked down the boy by midday after he ran away.

The mother, 42, was found dead in the corrugated iron-shack the family lives in, while the three-month-old sister was found dead in a nearby field.

The granny, 58, and brother, 7, died in hospital.

The murder weapon is still missing.

Police haven't disclosed a possible motive, but community members told radio's Eyewitness News the murders may have been part of a satanic ritual.

The teen's family told the radio they have disowned the boy.

"Even now I can't cope, because I have to take the kids and they have to stay with me," an uncle said.

"There is no other family member. They are all dead."

South Africa has one of the highest murder rates outside war zones.

Just under 16,000 people were killed between 2011 and 2012, according to official statistics.