Paris, France - Taiwanese boxer Lin Yu-ting became the second fighter at the center of a rightwing-fueled Paris Olympics gender controversy to guarantee herself a medal after convincingly winning her quarter-final on Sunday.

Lin, who together with Algerian boxer Imane Khelif is at the center of a storm over their eligibility, defeated Bulgaria's Svetlana Staneva on a unanimous points decision to reach the semi-finals of the women's 57kg category.

With her second win of the tournament, the 28-year-old Lin is certain to win a medal because losing semi-finalists in the boxing take home bronze.

After a scrappy and tetchy fight, the 34-year-old Staneva made an X sign with her fingers to the crowd and, clearly angry, declined to speak to reporters.

But her coach, Borislav Georgiev, held a piece of paper with the words: "I'm XX. Save woman sport."

In most cases, males have both an X and Y chromosome, while females have two X chromosomes.

The Bulgarian sign was seen as a dig against Lin and Khelif, both of whom have suffered fierce backlash amid lies suggesting they are not women. Neither athlete identifies as transgender or intersex.

The chief of the International Boxing Association (IBA) who claimed to a Russian state-owned news agency that both women tested positive for XY chromosomes has not released any evidence, nor have his remarks been substantiated.

Khelif, who boxes again on Tuesday, is also guaranteed at least bronze after winning her quarter-final on Saturday in the women's 66kg division.

Khelif and Lin were disqualified from last year's world championships after failing gender eligibility tests, but were cleared to box in the French capital. They also competed at the Tokyo Games in 2021 but did not win medals.

Lin will face Turkey's Esra Yildiz Kahraman on Wednesday in the semi-finals.

The Taiwanese athlete said she appreciated the support from people back home, where she has had the public backing of the government and fans.

"I just know that everyone is cheering for me, and I know that all the people in Taiwan are behind me and support me," she said.

The controversy ignited on Thursday when Khelif needed just 46 seconds to win her opening bout in the French capital, with her tearful Italian opponent Angela Carini abandoning the match.

Carini collapsed to the center of the ring in tears.

Lin and the 25-year-old Khelif were disqualified from the 2023 world championships, run by the IBA.

The IBA said this week that the two boxers "did not undergo a testosterone examination but were subject to a separate and recognised test, whereby the specifics remain confidential."

The boxing in Paris is organized by the International Olympic Committee (IOC), which took over due to widespread accusations of corruption at the IBA, including governance, financial and ethical issues.

The IOC has leapt to the defense of Khelif and Lin, with president Thomas Bach on Saturday saying they were born and raised as women and have passports saying that. Khelif's father has appeared in a video on social media showing his daughter's birth certificate listing her as female.