A mob set alight and killed an elderly couple who were accused of practising witchcraft in Lindelani near Ntuzuma, KwaZulu-Natal police said on Thursday.
"We were called in at 1am on Wednesday because a house was burning," Captain Thulani Zwane said.
He said they found Elsa Dubazane, 60, dead in her bedroom and her husband Rafael Dubazane, 66, dead on the road.
Police were investigating a case of murder. No arrests had been made.
The Mercury reported that the couple was attacked and assaulted on Friday by a mob which accused them of killing their granddaughter and burying her in the yard.
"Their granddaughter died at Mahatma Gandhi Hospital on January 4. She had overdosed on some pills because she was having family problems," Zwane said.
He said police were waiting for the results of a post mortem as there were allegations that Zakude Shozi,16, had been beaten by either her grandmother or her father.
