Barcelona have received a complaint from Atletico Madrid filed with FIFA over allegedly tapping up Julian Alvarez, a source from the Catalan club told AFP on Thursday.
Argentina striker Alvarez said during the World Cup it would be "the best thing for everyone" for Atletico to let him leave, amid strong Barca transfer interest.
Atletico believe Barcelona made prohibited contact with the 26-year-old attacker to encourage him to force his departure.
Barca president Joan Laporta said at the start of July his side had made an offer to Atletico for Alvarez which they would leave on the table for as long as they see fit.
Spanish media reported Atletico have also filed a complaint to the Spanish football federation (RFEF), but the RFEF did not respond to an AFP request for comment.
Atletico rejected an offer of €150 million from Real Madrid for Alvarez in June, widely viewed as a gambit by Los Blancos chief Florentino Perez to complicate a potential deal for Barca and fulfil a pledge made in his election campaign.
Barcelona are hoping to replace veteran striker Robert Lewandowski, who left at the end of last season, by adding Alvarez to their squad.
Alvarez joined Atletico from City in 2024 for a deal worth up to €85 million.