Zimbabwe’s first lady, Grace Mugabe, is alleged to have attacked a 20-year-old model at a hotel in South Africa, local media there report.
The woman accused Mrs Mugabe, 52, of hitting her in the face and put images of a head wound on social media.
The attack is said to have happened on Sunday evening at a hotel in the upmarket Sandton area of Johannesburg.
A provincial government minister said a case of assault had been opened by the alleged victim.
The reason for the alleged attack is not clear.
Zimbabwe Information Minister Christopher Mushowe told the BBC that he was unaware of the allegation.
Mrs Mugabe was in South Africa to be treated for an ankle injury, sustained during a freak road accident last month, when the alleged assault took place, according to Zimbabwean media.
Because she was in South Africa on a private visit, it is thought Mrs Mugabe may not protected by diplomatic immunity.
Gauteng province’s minister for community safety, Sizakele Nkosi-Malobane, said she had instructed law enforcement agencies to investigate the case “and ensure that justice is served”.
Mrs Mugabe has not yet commented.