Barcelona have received a two-window transfer ban from Fifa for breaching rules over "transfers of minors".
The Spanish champions have been found to be in breach of the signings of 10 minor players and have "committed several other concurrent infringements in the context of other players", according to world football's governing body. The Spanish Football Federation (RFEF) have also been sanctioned.
Fifa's sanctions follow investigations conducted by transfer matching system officials into under-18 players who were registered and participated in competitions with Barça between 2009 and 2013.
They cannot buy or sell players until the summer of 2015, and have also been fined £305,000. It was reported last month Barça had agreed a deal for Borussia Mönchengladbach's German goalkeeper Marc-André ter Stegen. Croatian 17-year-old Alen Halilović, who turns 18 in June, was scheduled to join them next season.
Barcelona have a trio of South Korean youth players, including the highly-rated 15-year-old striker Lee Seung Woo, plus other footballers from Africa.
Barça's ban could have major ramifications for a club many consider to be in a steady decline, despite their recent Clásico win at Real Madrid.
Barcelona will have to score at the Vicente Calderón to reach the Champions League last four
Atlético Madrid secured a 1-1 draw at Camp Nou in the clubs' Champions League quarter-final on Tuesday night and are favourites to eliminate the Blaugrana, while doubts persist over Barça coach Tata Martino, hired in the summer.
The inspirational Andrés Iniesta is also out of contract in 2015, as Pep Guardiola's dream team is slowly dismantled.
Their ban is just the latest stormy chapter during a turbulent campaign in which former president Sandro Rosell resigned over the allegation he misappropriated funds from the signing of striker Neymar, which the club were charged with tax fraud over.
Chelsea received a two-window transfer ban by Fifa in 2010 over the signing of Gael Kakuta, but won their appeal at the Court of Arbitration for Sport.
However, Chelsea reached a settlement with Lens for £1 million and the French club dropped charges, whereas Barça's case involves 10 players and multiple breaches.