Zimbabwe's first lady Grace Mugabe returned home on Tuesday from South Africa after failing to turn herself in to police in Johannesburg to face accusations of assaulting a model in a hotel room.

There was no immediate public comment on the case from Grace, 52, a possible successor to her husband President Robert Mugabe, 93, who has ruled Zimbabwe since 1980. But Zimbabwe government sources confirmed she had returned home.

"Yes, she is back in the country. We don't know where this issue of assault charges is coming from," said a senior government official, who declined to be named because they were not authorised to speak to the press.

A second official also confirmed that Grace had returned, saying "she is around now" and accused the media of a plot to tarnish the first family's name.

Earlier, South African police had been negotiating with Grace's lawyers to get her to turn herself in to face charges of assault in a court room, a senior police source said.

Twenty-year-old Gabriella Engels told South African media Grace had attacked her after the model had gone to see the Mugabes' sons Robert and Chatunga at a hotel in Johannesburg's upmarket Sandton district on Sunday.

Confusion surrounded the case on Tuesday. South African police minister Fikile Mbalula said early in the day that Grace had already handed herself in to police and would appear in court shortly.

But in the afternoon, the magistrates' court where police said Grace would be formally charged closed for the day without her appearing.

The police source said Grace had earlier agreed to hand herself over at 10 a.m. but failed to do so.

The source said police were investigating allegations of assault with intent to do grievous bodily harm.

The source said Grace Mugabe was not being considered a fugitive because no arrest warrant had been issued.

"One cannot be a fugitive for not appearing at a court to which they have not been summoned & when they have not been charged of any crime!" Jonathan Moyo, Zimbabwe's higher education minister and a close ally of Grace tweeted.

South African media said Grace had been in the country to have an injured foot examined. It was unclear whether she was travelling on a diplomatic passport.

FOREHEAD GASHED

A Zimbabwean intelligence source said Grace had been travelling on an ordinary non-diplomatic passport and was in South Africa on personal business.

The News24 website quoted Engels' version of events in the hotel room. "When Grace entered, I had no idea who she was. She walked in with an extension cord and just started beating me with it," the model said.

"She flipped and just kept beating me with the plug. Over and over. I had no idea what was going on. I was surprised ... I needed to crawl out of the room before I could run away."

News24 published a picture of what it said was Engels with a large gash in her forehead. "I am a model, with this scar over my face my whole career is ruined," she said.

It was unclear what triggered the incident.

"I just want justice," Engels told Talk Radio 702.

"She just completely lost it. I was hit all over my body. I have bruises all over my body ... I have two open wounds at the back of my head as well."

Mugabe's two sons were asked to leave the Regent luxury apartment complex in Sandton last month after an incident in the middle of the night, staff at the complex told Reuters.

Regent manager Imelda Fincham did not elaborate but confirmed the pair had left. "They're no longer here," she said.

In 2009, a press photographer in Hong Kong said Grace and her bodyguard had assaulted him. Police there said the incident was reported but that no charges were brought.

President Mugabe spoke at a public event marking Defence Forces Day in Harare on Tuesday, but did not mention Grace.

Grace was in the news in late July when she challenged her husband to name his preferred successor.

The issue of who will succeed Mugabe has deeply divided Zimbabwe's ruling ZANU-PF party. One faction supports Grace and the other Vice President Emmerson Mnangagwa, who is recovering in a South African hospital after he fell ill and was airlifted from Zimbabwe.