Princess Charlene of Monaco was in stable condition Friday after collapsing and being hospitalised in South Africa, her foundation said.

The 43-year-old South African wife of Prince Albert of Monaco, 43, was admitted to a hospital in the port city of Durban in the southeastern KwaZulu-Natal province on Wednesday night under an alias, after suddenly "collapsing" at a lodge where she has been staying for several months.

"Her Serene Highness (HSH) Princess Charlene of Monaco was rushed to hospital by ambulance late Wednesday night after collapsing due to complications from the severe ear, nose, and throat infection she contracted in May," the statement said.

"The Princess' medical team is currently evaluating her but have confirmed that the Princess is stable," it said.

Chantell Wittstock, director of the Princess Charlene of Monaco Foundation, later told AFP that "she has been released. She was released this morning".

"Doctors are still establishing exactly what happened," she said.

The Zimbabwean-born princess underwent surgery in August, but few details have been publicly released.

Her latest health scare was "part of the recovery," Wittstock said. "She has been in a lot of pain."

Former Olympic swimmer 

The former South African Olympic swimmer married Prince Albert II in 2011. 

One of Charlene's first public appearances with Prince Albert II was at the 2006 Winter Olympics in Turin.

Their son Jacques is now next in line to head the 700-year-old House of Grimaldi.

In recent weeks, lifestyle magazines across Europe have speculated feverishly that the royal couple could be headed for divorce.

Princess Charlene has been in South Africa for most of this year, saying she was forced to stay for medical reasons, although media reports suggests she is looking for a house there.

Her last public appearance with Albert in Monaco was in January. On August 25, she posted on Instagram, pictures with her husband and children.

After they were married, there were rumours, denied by the royal palace, that Charlene had even tried to escape on the eve of her marriage to Albert as well as claims she only agreed to go ahead with the wedding once he agreed to an exorbitant divorce settlement if she still wanted to leave.

Albert, 63, is the son of Prince Rainier III and Grace Kelly, an American film star who died in a car accident in 1982.

Born Charlene Wittstock on January 25, 1978, in Zimbabwe's second city of Bulawayo, Charlene's family moved to South Africa when she was 10 and they settled in the town of Benoni, in the outer reaches of Johannesburg's suburbs.

She took to the pool at the age of three, aided by her mother Lynette, a swimming coach and competitive diver. 

Swimming soon took over her life and her prowess became clear in the late 1990s as she claimed several national titles and competed for South Africa at the 1998 Commonwealth Games in Kuala Lumpur and again in 2002 in Manchester.

At the 2000 Sydney Olympics, Wittstock was on a women's relay team that finished fifth.