FIFA has received a complaint from Atletico Madrid over an alleged illegal approach from Barcelona for Antoine Griezmann.
The striker is one of Europe's biggest stars and extended his contract with Atletico during the summer until June 2022.
Griezmann has also been strongly linked with a move to Manchester United but Barcelona president Josep Maria Bartomeu is believed to have met with the Frenchman's family.
Barcelona's director of institutional relations Guillermo Amor did not deny the claims, saying: "Maybe there's been a meeting and things have advanced, although I don't know. There's a good understanding, maybe there have been talks. Rumours are inevitable in football.
"In the case of Griezmann, there are a lot of players we could be talking with, initiating some kind of relationship. We're obliged to have contact with players."
Griezmann, 26, joined Atletico from Real Sociedad in August 2014 and has averaged more than a goal every other game in La Liga.
Atletico boss Diego Simeone has said Griezmann could leave with his blessing if a "unique opportunity" came along.
He said: "I love watching my players grow, and if one of them tells me that they have the unique opportunity of playing for a certain team, after they did everything they could for me, like Griezmann has done, I'll say it's not a problem."