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A large crowd at Tehran airport greeted an Iranian sport climber considered a "heroine" by many for having competed with her hair uncovered.
Elnaz Rekabi, 33, defied Iran's strict dress code - but said her hijab had fallen off "inadvertently".
However many are sceptical about the explanation given on her Instagram, believing it was written under duress.
Iran is currently gripped by protests against compulsory hijab laws and the nation's clerical establishment.
Iranian women are required to cover their hair with a hijab and their arms and legs with loose clothing. Female athletes must also abide by the dress code when they are officially representing Iran in competitions abroad.
Ms Rekabi flew in from South Korea before dawn on Wednesday, where she had been competing at the Asian Championships.
Her family met her at the airport, where she was hugged and handed several bunches of flowers.
Videos on social media show hundreds of supporters clapping and chanting "Elnaz is a heroine" as she arrived.
Ms Rekabi has been hailed as a new symbol of the protests led by women in Iran.
Following the release of a video showing her competing without a hair covering, Ms Rekabi's friends said they could not contact her, and they raised concerns over her safety.
On Tuesday a post on her Instagram account appeared, in which she apologised for "getting everybody worried".
"Due to bad timing, and the unanticipated call for me to climb the wall, my head covering inadvertently came off," she explained.
She repeated this in a brief interview with state media on arrival in Tehran, adding that she was feeling "tense" about returning home.
Where she was taken after the airport is unknown.
BBC Middle East Editor Sebastian Usher says her reappearance in public may allay fears that she might be arrested, but many will want further reassurance.
In the past, female Iranian athletes who competed abroad without wearing a hijab have said they were forced by the authorities to issue similar apologies. Some decided not to go back to Iran.
Ms Rekabi's Instagram post said she was returning to Iran "alongside the team based on the pre-arranged schedule".
BBC Persian's Rana Rahimpour says that to many people the language used in this post looks like it has been written under duress.
The nationwide protests in Iran were sparked by the death in custody of Mahsa Amini, a 22-year-old woman arrested by morality police in Tehran on 13 September for allegedly wearing her headscarf too loosely.
The police denied reports that she was beaten on the head with a baton and said she suffered a heart attack.
The Iranian embassy in South Korea strongly denied what it called "all fake news, lies and false information" about her, and said Ms Rekabi had left Seoul for Iran on Tuesday morning.
A source told BBC Persian on Monday that Ms Rekabi's passport and mobile phone were confiscated, and that she left her hotel in Seoul two days before her scheduled departure date. Her family and friends lost contact with her after she said she was with an Iranian official.
The International Federation of Sport Climbing (IFSC) said it had been in contact with her and the Iranian Climbing Federation, and that it was "trying to establish the facts".
"It is important to stress that athletes' safety is paramount for us and we support any efforts to keep a valued member of our community safe in this situation," it added. "The IFSC fully support the rights of athletes, their choices, and expression of free speech."