UEFA withholds Atletico Madrid's prize money
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.
No clubs from the English Premier League, German Bundesliga, Italy's Serie A or France's Ligue 1 were among the named.
UEFA approved the introduction of the far-reaching FFP 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.