Real Madrid and Atletico Madrid have been banned from registering new players for the next two transfer windows, FIFA has announced.
The FIFA Disciplinary Committee announced that the two clubs "violated several provisions concerning the international transfer and first registration" of players under the age of 18.
They are permitted to sign players in the current transfer window but are set to be banned from making additions to their squads until after the 2016-17 season.
The statement from world football's governing body added: "Both clubs are to serve a transfer ban that prevents them from registering any players at national and international level for the next two complete and consecutive registration periods for breaching articles 5, 9, 19 and 19bis as well as annexes 2 and 3 of the Regulations on the Status and Transfer of Players (the 'Regulations').