"We are aware of that tragedy and deeply regret it", a Federation Internationale de Football Association statement said.
Sahar Khodayari's favorite soccer team was playing on a spring night in Iran's capital, Tehran, and she made a decision to sneak into the city's main stadium for a glimpse.
Khodayari was discovered, arrested and detained.
The semi-official Shafaghna news agency reported today that a 30-year-old woman identified only as Sahar died at a Tehran hospital.
Iran has come under pressure from Federation Internationale de Football Association to allow women to attend qualifiers for the 2022 World Cup, and was reportedly given a deadline of Aug 31 to comply. While at court to pick up a cellphone, Khodayari reportedly overheard "that if she were convicted she could get six months to two years in prison", per the BBC.
Sahar was bipolar, according to her sister, who was interviewed by Rokna, a local news outlet, on Wednesday.
However, she was arrested on the charge of "improperly wearing hijab" and jailed for three days before being released on bail.
Former Bayern Munich midfielder Ali Karimi - who played 127 matches for Iran and has been a vocal advocate of ending the ban on women - urged Iranians in a tweet to boycott soccer stadiums to protest Khodayari's death.More news: After another nightmare in New England for the Steelers, now what?
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No verdict had yet been delivered in her case.
The Iranian-Armenian soccer player Andranik "Ando" Teymourian, the first Christian to be the captain of Iran's national squad and an Esteghlal player, said in a tweet that one of Tehran's major soccer stadiums would be named after Khodayari " in the future".
Parvaneh Salahsouri, a reformist lawmaker, said Sahar was "Iran's girl".
In this photo from December 9, 2011, supporters of Iranian soccer team Esteghlal, hold flags of their favorite team, at the Azadi (Freedom) stadium, in Tehran, Iran.
However, that has drawn criticism from human rights activists overseas, as well as at home.
Women in Iran have been banned from going into stadiums to watch men's sporting events since 1981, according to Human Rights Watch.
Soccer's governing body Federation Internationale de Football Association, which has been pressuring Iran over the ban, regretted the "tragedy" of Khodayari's death.
While a small number of Iranian women have attended select global matches on previous occasions, others have faced prosecution for entering stadiums at other times.
"What happened to Sahar Khodayari is heart-breaking and exposes the impact of the Iranian authorities' appalling contempt for women's rights in the country", Philip Luther, Amnesty's Middle East and North Africa research and advocacy director, told the Associated Press.