Zimbabwe has blocked flights by South Africa's government-owned airline as tensions rise over allegations that Zimbabwe's First Lady assaulted a young model at a luxury hotel in Johannesburg.
South Africa's government said it had not yet decided to grant the Zimbabwe government's request for diplomatic immunity for Grace Mugabe, who has not commented on the allegations.
Local media reported that Mugabe was expected to attend a regional summit with 93-year-old President Robert Mugabe in South Africa's capital, Pretoria, in what would be her first public appearance since the alleged assault Sunday night. But there was no sign of her as of midday.
Twenty-year-old model Gabriella Engels has claimed that Ms Mugabe whipped her with an extension cord, cutting her forehead. Lawyers for Ms Engels have threatened to go to court if immunity is granted.
Foreign ministry spokesman Nelson Kgwete said in a text message to The Associated Press on Saturday that South Africa was still considering the request.
"Decision yet to be made," Mr Kgwete said.
South African police have issued a "red alert" at borders to ensure Ms Mugabe doesn't leave undetected. Police also say their investigation is complete but needs a government decision on the immunity appeal.
South African Airways said Zimbabwe had placed restrictions on its operations, affecting its flights between the neighbouring countries.
In a statement, the South African government-owned airline said its flight from Zimbabwe's capital to Johannesburg was unable to take off as scheduled Saturday morning. Another flight from Johannesburg to Harare has been cancelled.
South African Airways said Zimbabwean authorities were demanding a "foreign operators permit" to allow the airline to operate in Zimbabwe. It said it has been flying to and from Zimbabwe for more than 20 years and that the permit was never required until Saturday morning.
The statement by the airline does not mention the allegations against Zimbabwe's first lady.
The scandal over Ms Mugabe is a sensitive issue for South Africa as it weighs the possible diplomatic fallout from neighbouring Zimbabwe if it acts against the First Lady - and the likely outrage at home if it grants immunity and allows her to leave.
Some demonstrators protested on Saturday in Pretoria against Mr Mugabe and his wife, saying she should be prosecuted.
It is not clear whether Ms Mugabe entered South Africa on a personal or diplomatic passport.