Dozens of emails released by the group, which is allegedly linked to the Russian security services, show separate conversations between officials from the World Anti-Doping Agency (WADA) and the United States Anti-Doping Agency (USADA).

This has already been dismissed by USADA, however, as "attempts to create fake news and smear their names in order to divert attention away from their [Russia's] own state-operated doping programme".

Unlike previous Fancy Bears leaks, the documents have not been placed on the hacking group's website but were reported on by newspapers in Britain.

According to The Times, topics include suggestions that high-profile American athletes submitted tests showing unusual blood values as well as a tip-off that at least two US Olympians took cocaine in order to lose weight before Rio 2016.

There are also reported suggestions that a non-American athlete, who has not been banned, had a blood transfusion before a major race.

More Therepeutic Use Exemptions (TUEs) awarded to British athletes allowing them to use otherwise banned products for medical reasons were also highlighted.

Sprinter Adam Gemili was reportedly given an exemption for a painkiller after tearing his hamstring at the Birmingham Grand Prix in June 2015. 

Rugby sevens player Emily Scott was also reportedly granted permission to use corticosteroids to treat rheumatoid arthritis.

There is no suggestion either broke any rules.

More than 100 athletes who competed at the Rio 2016 Olympic Games have been named as having obtained TUEs by Fancy Bears in recent months.

It has led to criticism of the TUE system and claims that use of them should be made fully public.

WADA has hired cyber security firm FireEye Inc to assess the extent of the data breach by Fancy Bears and to improve its defences to avoid a future attack.

But the organisation has contested the need for reform to the TUE system and defended athletes' right to medical privacy.

"The confidential information that has been sent to journalists [by Fancy Bears] comes from the same breach to WADA’s system that took place in August 2016," a WADA spokesperson told insidethegames.

"The criminal leak of this information - which is regular correspondence on anti-doping operational matters from WADA staff - illustrates nothing new, and is once again part of a continued effort to discredit WADA and the broader anti-doping system. 

"Furthermore, this activity is part of an attempt to distract from the real issue: the serious breaches to world anti-doping rules that were evidenced in the McLaren Report.

"WADA will be corresponding with the affected athletes, law enforcement authorities and relevant anti-doping organisations so that they are aware of the possibility of this confidential information entering the public domain."

USADA spokesperson Ryan Madden blamed Russia for using Fancy Bears as an "attempted distraction".

"While in a lot of ways these emails only further demonstrate the high standard to which athletes in the US are held, what is concerning to us - as well as anyone else who truly values the spirit of Olympism - is the clear and malicious violation of athletes’ rights," he told insidethegames.

"What we hope doesn’t get lost in the headlines is that these athletes have done everything asked of them, have been held to the highest standard and are now being forced to watch as a cyber-espionage group attempts to create fake news and smear their names in order to divert attention away from their own state-operated doping programme. 

"It’s abhorrent and we hope that the international community will come together, support these athletes and do whatever it takes to put an end to this ugly behaviour."