JOHANNESBURG – Thousands of people welcomed South African runner Caster Semenya on her return to Johannesburg airport on Tuesday, as local athletics officials slammed the decision to test the champ's gender.

Semenya smiled broadly and said "Hi everybody" as she arrived at the airport along with her teammates, while people sang and danced in the corridors and fans hung over railings and crowded around windows to catch a glimpse of her.

Supporters waved home-made placards which read "Our first lady of sport" and "100 percent female woman", cheering her and her gold medal at the World Athletics Championships.

Semenya said nothing else throughout the celebrations and an hour-long press conference that followed, where top politicians and athletics officials denounced the International Association of Athletics Federations (IAAF) decision to verify her gender.

IAAF made the announcement shortly before the 18-year-old powered to a 1minute 55.45seconds win in the 800 metres -- the world's best this year -- in Berlin last week.

Athletics South Africa again denied criticism that it failed to prevent the global controversy by quashing any doubts about her gender ahead of the competition.

"Athletics South Africa, we did not have any information that people are doubting," ASA president Leonard Chuene told journalists.

South Africans have rallied behind Semenya in a national show of support. Her arrival was broadcast live on television, while police made special traffic arrangements around the airport to accommodate the crowds.

Women wearing brightly coloured traditional dress typical of her region in rural Limpopo province blew horns and waved South African flags as she entered the airport.

Semenya arrived along with fellow gold medalist Mbulaeni Mulaudzi, long jump silver medalist Khotso Mokoena, who will later meet President Jacob Zuma in Pretoria, where the athletes will parade through the streets.

The gender-testing debate has sparked outrage in the 18-year-old's home country, with the ruling party and its youth and women's wings calling the tests "sexist and racist".

"Caster is a girl...I am not worried about that too much. Caster is like my child. I know where she comes from. For myself, I know Caster is a girl," her uncle Ben Semenya told AFP at the airport.

"I think it was unfair," said Amo Moroka, a physician who was among the crowd.

"On the date of her final, that is when they decided to test her. There were midwives and parents that raised her. They are undermining South Africa as a country," the doctor said.

Semenya's return was given top coverage by local media, with The Times newspaper running a wrap-around souvenir poster headlined "Welcome home Caster, our champ" with a life-sized portrait of the 18-year-old.

The gold medallist's deep voice has raised questions about her gender her entire life, according to her family.

But the IAAF says it was her rapid speed gains this year that prompted the gender test, which will take weeks to complete and include physical, medical, and psychological examinations.

The furore has seen countless debates over often grey areas of gender, chromosomes and hormones, and what makes a woman a woman, in a debacle which has overshadowed one of the best performances by a South African athlete in recent years.

"At the end of the day she is our hero. She is our African girl and we do not need to question that," said Michael Masdmola from Limpopo, cheering at the airport.