Real Madrid have been fined €30,000 (£24,750) by UEFA due to 'discriminatory behaviour' apparently witnessed during their 3-1 win over Manchester City.
It is not clear precisely what prompted the punishment, but it is understood to be the result of the actions of a group of fans at the Bernabeu during the second leg of Madrid's 6-3 victory in the Champions League's playoff round.
In addition to the club's fine, Madrid have been warned by European football's governing body that further bad behaviour could result in a partial stadium ban.
UEFA will order at least 500 seats to be closed for a future European match if there is a repeat offence in the next two years.