Olympics in shock as US star Simone Biles PULLS OUT of gymnastics team final in Tokyo

American gymnastics icon Simone Biles has pulled out of the final of the artistic all-round team event in Tokyo, with conflicting reports on the health of the 24-year-old star.

Four-time Olympic gold medalist Biles left the floor at the Ariake Gymnastics Centre after her opening vault before returning with her tracksuit on. 

Initial reports indicated that the withdrawal was injury-related, although reports online citing broadcaster NBC later suggested the issue was related to Biles' mental health.

However, in an official statement, USA Gymnastics said: "Simone Biles has withdrawn from the team final competition due to a medical issue. She will be assessed daily to determine medical clearance for future competitions." 

Despite her own early exit, Biles was still seen encouraging her teammates from the sidelines. 

The Americans are bidding to win a third straight gold medal in the event, but finished second behind the Russian team in qualifying. 

The loss of Biles will be a huge blow for her team's chances, even though the usually flawless star appeared to struggle during qualifying, making some rare missteps. 

Biles is among the biggest names at this year's Tokyo Games, even getting her own 'GOAT' emoji in a nod to the legion of fans who believe her to be the greatest female gymnast of all time. 

Biles was forced to watch on as her team competed. © Reuters

However, Biles has also alluded to the pressure she is under, writing on social media after qualifying: "I truly do feel like I have the weight of the world on my shoulders at times.

"I know I brush it off and make it seem like pressure doesn't affect me but damn sometimes it's hard hahaha! The Olympics is no joke!" she added.

Concerns will now focus on the state of Biles' health and what that means for her participation in the individual events in Tokyo.