Europa League winners Atletico Madrid were among 23 clubs to have prize money withheld as European football's governing body UEFA revealed the first sanctions under its financial fair play rules today.
UEFA said the clubs, who also include Qatari-owned La Liga side Malaga and Portugal's Sporting, were found to have "important" overdue payments to other teams, their own employees or social and tax authorities.
As a result their money for taking part in European competition would be withheld pending further investigation, UEFA said in a statement.
The clubs will have to provide an updated report on September 30 to a UEFA committee led by former Belgian Prime Minister Jean-Luc Dehaene.
"This ... measure will remain in force until all identified balances have been settled in full or until a final decision by the (UEFA committee) is taken," said UEFA.
Among other clubs under investigation are Dinamo Bucharest and Rapid Bucharest of Romania, Turkey's Fenerbahce and Serbia's Partizan Belgrade.
All are involved in this season's UEFA competitions.
There were no clubs from the English Premier League, German Bundesliga, Italy's Serie A or France's Ligue 1 among the clubs named.
UEFA approved the introduction of the far-reaching financial fair play rules in 2009 in a bid to reduce debt and introduce better and more transparent financial dealings among clubs playing in its competitions.
UEFA president Michel Platini said the measures have been introduced to stop clubs from spending their way into oblivion and to force them to live within their means.
They are also intended to stop wealthy owners from trying to buy success with limitless spending on players, distorting the transfer market in the process.
Transfer fees and outgoing payments have been monitored since the start of the 2011/12 season with clubs tasked with breaking even in 2012 and 2013 and being assessed during the 2013/14 season.
If clubs have not come into line by then, they could be thrown out of European competition.