Caster Semenya appeared to take aim at the IAAF in a social media post after a new ruling on hyperandrogenism was introduced.

Athletics' governing body have brought in new regulations affecting women with higher than normal levels of testosterone who compete in track events ranging from the 400 metres up to a mile.

Two-time Olympic gold medallist Semenya is among the athletes who will still be eligible to compete, but only provided testosterone levels are reduced to below five nmol/L for a continuous period of at least six months.

The ruling states that a blood testosterone level below five nmol/L must be maintained continuously - whether in competition or out of competition - for so long as she wishes to remain eligible.

South African three-time 800m world champion Semenya seemed to respond to the news with a tweet including an emoji showing a stern face, accompanied by the message: "I am 97 per cent you sure you don't like me, but I'm 100 per cent sure I don't care."

IAAF president Sebastian Coe said in a statement: "We want athletes to be incentivised to make the huge commitment and sacrifice required to excel in the sport, and to inspire new generations to join the sport and aspire to the same excellence.

"As the International Federation for our sport we have a responsibility to ensure a level playing field for athletes. Like many other sports we choose to have two classifications for our competition – men's events and women's events.

"This means we need to be clear about the competition criteria for these two categories. Our evidence and data show that testosterone, either naturally produced or artificially inserted into the body, provides significant performance advantages in female athletes.

"The revised rules are not about cheating, no athlete with a DSD [Difference of Sexual Development] has cheated, they are about levelling the playing field to ensure fair and meaningful competition in the sport of athletics where success is determined by talent, dedication and hard work rather than other contributing factors."