Atletico Madrid have released a statement claiming Barcelona have not paid a sufficient transfer fee for Antoine Griezmann.
Barcelona parted with €120m to sign the France international after July 1, when his €200m contract release clause was slashed by a staggering €80m.
But Atletico claim Barcelona and Griezmann reached a deal before this date, and that they are subsequently owed the amount of his original release clause.
Atletico Madrid posted a brief statement to social media shortly after Barcelona confirmed the signing of Griezmann on a five-year deal.
The statement reads: "Antoine Griezmann, represented by his lawyer, has appeared in the headquarters of the Professional Football League to terminate his contract with Atletico Madrid as Barcelona have paid on behalf of the player the amount of €120m.
"Atletico Madrid believe the amount paid is insufficient to meet the release clause, because it is obvious that the player and Barcelona had agreed terms before the release clause was reduced from €200m to €120m.
"It was also agreed before the date in which the clause was modified on May 14, when Griezmann announced he would be leaving the club.
"Atletico Madrid believe the termination of the contract occurred before the end of last season due to the events, acts and demonstrations carried out by the player and that is why the procedures have started that are considered appropriate for the defence of our rights and interests."
