Hardcore fans of Lazio football club in Italy have circulated a letter saying women should be banned from part of the Curva Nord of Rome's Olympic Stadium.
The Lazio ultras have gained a reputation for violence, racism and anti-Semitism.
Before the first game of the season, an unofficial flyer was handed round saying the stand was a "sacred place" where women were not allowed.
But Lazio blamed "a few fans". "We are against any discrimination," it said.
Lazio spokesman Arturo Diaconale, quoted by Italian media, said "we didn't know anything about this [flyer], it was an independent initiative by some of the Curva Nord fans".
"It's not the position of society... There is a huge number of Lazio fans, whereas this is an initiative from a few fans. We cannot always intervene to prevent politically incorrect demonstrations like this one."
The ultras' flyer said women should go to other parts of the stadium.
The pamphlet called for "women, wives and girlfriends" to avoid the first 10 rows of the stand.
"Those who choose the stadium as an alternative to the carefree and romantic day at the Villa Borghese [a Roman historic house and park], should go to other parts," it read.
The flyer is signed "Direttivo Diabolik Pluto", who is one of the leaders of a group of Lazio ultras known as the Irreducibili.
Last season the club was fined after supporters displayed anti-Semitic stickers showing Holocaust victim Anne Frank in a Roma shirt.
A group of women fans from the Curva Nord, quoted by the Italian football website calcioweb.eu, expressed "indignation" over the ultras' flyer telling women to sit elsewhere.
They said the Curva Nord had a "sacred role", and "we distance ourselves from those Lazio fans whose inappropriate behaviour lowers the Nord's value".
"And we distance ourselves from those whose gestures and words show they have forgotten that it was a woman who gave birth to them."
Carolina Morace, coach of the AC Milan Women's First Team, said those who wanted to ban women from the first 10 rows of the Curva Nord "should be banned from the stadium". "Sexism is also violence," she said.
Quoted by the daily Il Messaggero, she said some social media comments on the Lazio controversy "lead one to think that there is not the slightest respect for women, for sportswomen, for their passion.
"The football world must help to overcome all forms of discrimination, not to exacerbate them, as happens all too often: I will always fight to ensure that stadiums are hospitable to everyone."
Manila Nazzaro, a Lazio fan who was Miss Italia '99 and is now a TV presenter, said "rules of the pack" were common to all fans, not just Lazio's.
"Some environments remain purely masculine, which men love to share with other men, just as there are some that women love to share with women."
She said that "in the collective's ideal the Curva is purely masculine". "When there were really ugly episodes like the Anne Frank stickers, I was the first to criticise. This time let's take it more lightly."