Atletico Madrid will be unable to sign new players until January 2018 after the Court of Arbitration for Sport (CAS) on Thursday upheld their transfer ban.

Atletico and city rivals Real Madrid were barred from registering new players for two transfer windows in January 2016 for irregularities in the signing of foreign players under 18.

"This ruling is unfair and causes an irreparable damage to our club," Atletico said in a statement.

Both Madrid based teams have been quite successful over the last 3 seasons. They have also featured prominently in the semi-finals of the UEFA Champions League.