Fiorentina have lodged an official complaint to FIFA over Mohamed Salah's loan move to Roma from Chelsea.
The Egypt international impressed during a short-term spell at the Stadio Artemio Franchi last season but opted to join Rudi Garcia's side for 2015-16, rather than return to Florence.
Viola president Andrea Della Valle threatened legal action prior to Salah completing his move to the capital, and the club have now taken the case to world football's governing body, alleging a breach of contract.
"We can confirm having received a claim from the Italian club, ACF Fiorentina, against the English club, Chelsea FC, and the player, Mohamed Salah Ghaly, for breach of contract," a FIFA spokesperson said, as quoted by The Guardian.
"The matter is still pending and being investigated."
Speaking on Friday, Jose Mourinho sarcastically claimed he was happy to see FIFA electing to take action on such issues.
"I'm happy that FIFA has time for other things in the middle of such great weather around them," the Chelsea boss told a press conference.
Get the best features, fun and footballing frolics straight to your inbox every week.
Thank you for signing up to Four Four Two. You will receive a verification email shortly.
There was a problem. Please refresh the page and try again.