“The badly injured baby was rushed to Tshilidzini hospital but was declared dead on arrival,” said Brigadier Hangwani Mulaudzi.
The incident happened at the Ha-Mutsha village outside Thohoyandou on Friday evening.
The 30-year-old mother was alleged to have tried to also kill the second twin.
“While the police were racing to crime scene, some frantic community members managed to rescue the other twin whom she allegedly wanted to kill, contained the mother, until she was detained by the police,” said Mulaudzi.
The surviving twin was doing well and was with the woman’s relatives.
Ngubane said the motive for the attack was unknown.
The woman was expected to appear at the Vuwani Magistrate’s Court on Monday.