The International Association of Athletics Federations (IAAF) has announced that it has decided to ban transgender people from competing in elite female championships, if they have gone through the male puberty stages.

The council also voted to tighten restrictions on athletes with differences in sexual development while halving the maximum plasma testosterone for athletes, to 2.5 nmol per liter instead of 5 nmol.

IAAF President Sebastian Coe told a news conference that "the decision to exclude transgender women is based on the urgent need to protect the female category."

The IAAF had previously floated the option of allowing transgender athletes to compete in the female category, if they also kept testosterone levels below 2.5 nanomoles per liter for 24 months.

However, the IAAF said it had become clear that there was little support within the sport for the proposal.

"We don't say no forever," Coe said, adding that the IAAF would set up a task force to study the issue of transgender inclusion, which would be chaired by a transgender athlete.

"The working group will consider any point of differentiation, change event or that enhances our understanding in this area. We don't know enough and now we need to know more, and that's the journey we're taking. But we were not willing to risk the female category on current foundations."

Athletes with differences in sexual development must lower their testosterone levels below the new limit for at least 24 months to compete internationally in any elite female tournament, the IAAF said in a statement.

The stricter rules will affect athletes with differences in sexual development such as two-time Olympic champion Caster Semenya in the 800, 2020 Olympic silver medallist Christine Mboma in the 200m and Francine Nionsaba who finished second behind Semenya in the 800m at the 2016 Olympics.

The International Athletics Federation's regulations on differences in sexual development previously required transgender competitors in races between 400 metres and miles to keep testosterone levels below 5 nanomoles per litre.

The IAAF has introduced temporary rules for athletes who will already compete outside of events restricted by the IAAF's rules, requiring them to lower their testosterone level to 2.5 nmol per litre for 6 months.

This would prevent many transgender people from competing at the World Championships in Athletics in August.