South African runner Caster Semenya, who is undergoing gender testing after questions arose about her muscular build and deep voice, returns home today to celebrations after her 800-metre win at the world championships.

South Africans have rallied behind the 18-year-old, who is not accused of trying to cheat but of perhaps unknowingly having a medical condition that blurs her gender and gives her an unfair advantage over other female runners.

The governing African National Congress party, unions and other groups were urging their members to come to the airport this morning to greet Semenya at a rally.

"I'll be there," Semenya's father, Jacob, said yesterday. He said his daughter would then return to university in Pretoria.

Jacob Semenya said it was not clear when his daughter would visit the family's village in northern South Africa. But Sammy Molofo, an ANC Youth League leader in the area where the runner grew up, said a weekend homecoming celebration was being planned there.

Despicable campaign

President Jacob Zuma was to meet Semenya and the two other South African medalists, men's 800-metre champion Mbulaeni Mulaudzi and men's long jump runner-up Kgotso Mokoena at the presidential guest house in Pretoria.

COSATU, the country's main trade union federation, said today's welcome would be for the whole team, but "especially Caster, who has been the victim of such a despicable campaign by international athletics officials to discredit her magnificent achievement by maliciously raising unfounded questions about her gender".

Semenya's family and friends say there is no doubt she is a woman. But it is not always easy to get a clear-cut answer from scientists on the question in some cases.

The IAAF, track and field's governing body, will decide Semenya's case according to whether her "conditions ... accord no advantage over other females" after consulting a gynecologist, an endocrinologist, a psychologist, an internal medicine specialist and a gender expert. Her genes and physiology as well as how she sees herself and how she is seen by her community could play a role in their determination.

South Africans have been outraged not just that questions have been raised, but that they have been made public.

On Sunday, Lamine Diack, the IAAF president, said the affair was handled badly.

"I deeply regret that confidentiality was breached in this case and that the IAAF were forced into a position of having to confirm that gender testing was being carried out on this young athlete,"