Barcelona president Josep Maria Bartomeu has denounced FIFA for punishing the La Liga club over a breach of rules on the transfer of foreign under-18 players, calling it a "grave injustice".

Soccer's world governing body announced on Wednesday it had banned the Spanish champion from the transfer market for two consecutive windows and fined it $504,700.

The Spanish soccer federation (RFEF) was fined $564,000 after FIFA found it had also breached rules on the transfer of minors.