Zimbabwe's first lady Grace Mugabe is requesting diplomatic immunity after being accused of assaulting a 20-year-old model, South African police say.

The wife of leader Robert Mugabe failed to appear at a police station on Tuesday to answer the charges, authorities said.

According to police, Mrs Mugabe did not make an appointment to receive a warning and present her side of the story, despite the meeting being rescheduled several times.

Public service broadcaster SABC reports that Mrs Mugabe has been accused of hitting Gabriella Engels with an extension cord.

The model is said to have been visiting the Mugabes' two sons Robert and Chatunga at a hotel in the Johannesburg suburb of Sandton when the alleged incident took place.

Acting National Police Commissioner Lesetja Mothiba said: "Our position was that she must go to court. The whole day yesterday we were waiting for her."

There were suggestions Mrs Mugabe could have fled South Africa, but police confirmed on Wednesday that she was still in the country.

In a statement, the South African Ministry of Police said: "The suspect remains in South Africa and has not departed the Republic.

"Discussions with the suspect's lawyers and the Zimbabwean High Commission representatives are taking place to make sure that the [suspect] is processed through the legal system."

Ministry of Police statement on #GraceMugabe pic.twitter.com/abUCQmBTYn

— eNCA (@eNCA) August 16, 2017