South Africa's athletics federation said on Thursday it would challenge new rules governing female athletes' testosterone levels, which affect the nation's Olympic champion Caster Semenya.

Athletics South Africa (ASA) said it would "challenge the International Association of Athletics Federations (IAAF) on these new regulations as we have found them to be skewed".

The new policy targets women who naturally produce unusually high levels of testosterone.

Athletes classified as "hyper-androginous" will have to chemically lower their testosterone levels to 5 nanomoles per litre of blood to be eligible to run any international race of 400 metres up to the mile.

The ASA said that, after consultation with South Africa's sports minister, it would take the IAAF to Lausanne's Court of Arbitration for Sport (CAS) if it did not rethink the rule.

The IAAF has defended the rule change as scientifically sound arguing that "hyper-androginous" women with heightened testosterone levels enjoy an unfair advantage.

But the rule has provoked fury in South Africa with officials and sports lovers describing it as "racist" and "sexist" and a deliberate attempt to target Semenya.

In its statement, the ASA commented that the IAAF had imposed similar rules around "hyper-androginous" athletes in 2011.

These were successfully appealed by an affected Indian athlete, Dutee Chand.

A study into female athletes with heightened testosterone levels, co-funded by the IAAF and the World Anti-Doping Agency, concluded that those affected had a "significant" advantage in certain competitions.