POLICE are on the hunt for a woman who yesterday killed her two-day-old baby boy by stabbing him in the chest and then abandoned three other minor children.

The woman, aged 31, allegedly killed her baby in a room she rents with her lover, the father of the children, in Booysens, Johannesburg. She has fled.

The child's body was found stuffed in a rubbish bin. It had a stab wound in the chest and head.

Neighbours believe the child was thrown against a hard object and this killed him.

The woman's three other children, aged, nine, seven and three, were found alone in their room. Neighbours have since taken the children from the house.

Queen Mti, who rents a room in the same house as the woman, said she made a shocking discovery of something wrapped in the dustbin "covered with blood".

She and her neighbour headed to the nearby Booysens police station and alerted the police, who found the body of the child.

Neighbours said the woman was last seen on Saturday morning. They suspect she could have given birth on Thursday in her room.

Steven Malindi, a younger brother of the woman's lover, called for the arrest of the suspect.

"That woman is cruel. How can she commit such a brutal crime? There is no mother who would kill her own blood," he said.

Malindi claimed that earlier last year he saw her trying to abort the child by drinking laxatives.

"She said she did not want the child. I told my brother Jimmy, and he did not listen to me ... "

He said on Thursday his brother told him the suspect had given birth to a baby boy and the child was later admitted to the Chris Hani Baragwanath Hospital in Soweto.

Malindi broke the news of the grissly find to Jimmy, who was in Thembisa, Ekurhuleni.

Warrant Officer Lorraine van Emmerik said they had opened an inquest docket.

"We are waiting for the results of the post-mortem, which will reveal the cause of death," she said. "At the moment we are also looking for the woman to ask some questions."