Gabriela Anelli, 23, suffered two heart attacks after she was hit outside the Allianz Parque while waiting to get in.

According to her brother Felipe, she was taken to hospital and operated on after being hit, and had previously had heart, lung and kidney surgery as a child.

Football club Palmeiras, who play at the Sao Paulo stadium, said on social media it "cannot accept that a 23-year-old woman be a victim of barbarism in a place that should be for entertainment".

It added it wanted the police to investigate what happened as it "hurts the image of Brazilian soccer".

On the same day, another incident took place in a different area of the stadium shortly before the woman was injured, causing the referee to pause the game so tear gas used by the police could dissipate.

Ednaldo Rodrigues, president of the Brazilian Football Confederation, said he was working with authorities "to avoid criminal and sad episodes like this from happening again".

"Just like in the issue of racism, it is enough (of violence)," he said in a statement.

"Soccer is about passion and not a place for infiltrated criminals to act with violence."

Santos FC, a fellow top flight Brazilian team, sent a message of solidarity, writing on Twitter: "The four clubs with the largest fans in Sao Paulo stand in solidarity with the family of Gabriela Anelli in this moment of immense pain.

"So we also embrace all the fans, family, athletes, professionals and football lovers saddened by this unfortunate episode. May this revolting case not be in vain.

"We, athletes, technical committees and fans want to see arenas and stadiums without fear, without violence, without discrimination or intolerance, with a healthy and fair rivalry on the pitch, in an environment in which joy prevails, such a striking feature of Brazilian football."