Italian boxer Angela Carini has apologized after quitting her bout at the Paris Olympics in 46 seconds, a viral moment that has led to online abuse of her Algerian opponent, Imane Khelif.

Khelif, a 25-year old light welterweight, landed a heavy first punch in Thursday’s bout with Angela Carini from Italy, dislodging her chinstrap. Subsequent blows pushed Carini back to her corner before she dropped to her knees. Following her loss to Khelif, Carini did not shake her opponent’s hand.

Some spectators watching the match later raised questions about Khelif’s participation, citing a 2023 decision by a now-discredited boxing regulator to bar her from a women’s tournament.

The International Olympic Committee (IOC) however strongly supports her participation in the 2024 Games, with IOC spokesperson Mark Adams saying she was “born female, was registered female, lived her life as a female, boxed as a female, has a female passport.”

“This is not a transgender case,” Adams added.

Carini apologized Friday for her treatment of Khelif. “I’m sorry for my opponent,” she told Italian outlet La Gazzetta dello Sport. “If the IOC said she can fight, I respect that decision.”

“It wasn’t something I intended to do,” Carini said. “Actually, I want to apologize to her and everyone else. I was angry because my Olympics had gone up in smoke,” she said.

The fight has, however, become a flashpoint for an often misinformed debate about how women are allowed to compete in sports. It also triggered an onslaught of online abuse, with transphobic commentators incorrectly calling Khelif “a man” because of an alleged physical advantage.

As Khelif prepares for her next fight on Saturday, here’s what to know:

Who is Imane Khelif?

Khelif is an accomplished amateur who won a silver medal at the International Boxing Association’s world championships in 2022.

But in March 2023, Khelif came under the spotlight for another reason: the IBA disqualified her from a gold medal match, saying that a test showed that she “did not meet the required necessary eligibility criteria” and was “found to have competitive advantages over other female competitors.”

The IBA, which was stripped of its recognition as the official boxing body for the Games by the IOC for corruption and financial related issues, also disqualified featherweight Taiwanese boxer Lin Yu-ting boxer for the same reason.

The IBA did not say what test the pair had been subjected to. “The athletes did not undergo a testosterone examination but were subject to a separate and recognized test, whereby the specifics remain confidential,” it said.

IOC spokesperson Adams dismissed the IBA’s test, calling it “arbitrary,” and said the pair were disqualified by the IBA “without any due process.”

Who is getting involved?

Khelif has been subject to a torrent of online abuse, with prominent anti-trans figures, right-wing commentators and politicians incorrectly calling Khelif a man – and using the controversy to fuel the wider culture war around gender identity.

Former US President Donald Trump, Elon Musk, JK Rowling and social media influencer-turned WWE wrestler Logan Paul have all weighed in. “Watch this then explain why you’re OK with a man beating a woman in public for your entertainment,” Rowling wrote on X, amplifying misinformation about Khelif’s gender.

Italy’s Giorgia Meloni, who was visiting Italian athletes in the Olympic Village on Thursday said that the competition “wasn’t an equal fight.” The right-wing Italian prime minister said that she has opposed allowing athletes with “genetically male” characteristics to compete against women since 2021.

Many athletes have written in support of Khelif, including Irish boxer Amy Broadhurst – who fought and beat Khelif in the World Championships. Broadhurst posted a picture of the pair before their 2022 match on X, saying: “Please, the hate has been ridiculous.”

The controversy has not only overshadowed Khelif’s victory but also has implications for her privacy and safety. For example, in her home Algeria, freedom of self expression is severely limited – and being gay or transgender is illegal.

Still, the Algerian Olympic Committee (COA) has strongly defended their athlete, saying: “Such attacks on her personality and dignity are deeply unfair, especially as she prepares for the pinnacle of her career at the Olympics.”

“The COA has taken all necessary measures to protect our champion,” it added.

What do we know about sex testing?

Sex testing in sports have come under scrutiny from groups like Human Rights Watch, who say that they violate fundamental rights to privacy and dignity.

The tests that the IBA claimed disqualified Khelif and Lin from competing in 2023 are confidential – so there is no way of knowing why exactly they were barred last year.

Female athletes that have differences of sexual development (DSD) are often subject to such tests. (Khelif, however, has not said she has DSD.)

DSD is a group of conditions involving genes, hormones and reproductive organs – and can be associated with a condition where a female body naturally produces more testosterone than others. DSD traits only become apparent at puberty, when secondary sex characteristics, such as facial hair, breast tissue or distinct body shapes start to develop.

It is difficult to estimate how many people have DSD traits – many live their entire lives without ever knowing they have one. Scientists estimate as many as one out of every 50 people is born with DSD traits. A person with DSD may have any gender identity.

Ahead of the Paris Games, the IOC introduced new rules and regulations relating to athletes with DSD.

The IOC rules say that inclusion should be the default in such cases and that athletes with DSD should only be excluded from women’s competition if there are clear fairness or safety issues.

The IOC reiterated Friday that all athletes competing in the boxing tournament “comply with the competition’s eligibility and entry regulations, as well as all applicable medical regulations.”

The IOC’s Adams added however that he understood concerns that had been raised around testing, fairness and safety.

“Everyone wants a black and white explanation of how we can determine this. That explanation does not exist neither in the scientific community nor anywhere else,” he said.

Are sex tests in sport new?

The policing of women’s bodies in sport is nothing new, with the practice of systemic medical examinations starting around the 1936 Berlin Olympics.

At the 1966 European Athletics Championships in Budapest, women underwent a visual examination of the genitals and secondary sexual features, carried out by a panel of three women doctors. The exams have been referred to as “nude parades.”

It was only in the 1990s, when blanket sex tests were dropped by many major sports bodies, including the IOC in 1999, which now conducts medical evaluations on a case-by-case basis.

South Africa’s double Olympic 800m track champion Caster Semenya, who has naturally occurring higher testosterone levels associated with DSD, remains front and center at this debate. Since 2019, she has been barred from competing in certain competitions under World Athletics regulations – unless she takes medications to lower her testosterone levels. Earlier this year she appeared at the European Court of Human Rights (ECHR) to continue her challenge against the sporting body.

Over the last few years, as the debate around women’s bodies in sport has grown, the governing bodies of athletics, cycling, swimming and rugby union have been tightening their regulations to exclude competitors who have gone through male puberty from women’s events.

CNN’s Saskya Vandoorne, Camille Knight, Natasha Maguder, David Close and Eliza Anyangwe contributed reporting.

For more CNN news and newsletters create an account at CNN.com