Fenerbahce was expelled from the Champions League for the second time in three seasons and Besiktas was banned from the Europa League after the Turkish clubs were punished by UEFA on Tuesday over separate charges of match-fixing.
Fenerbahce was banned from the next three UEFA club competitions for which it would have qualified, starting with next season's Champions League, in relation to a long-running fixing case that dates back to the Istanbul club's league-winning run in 2011. UEFA said the sanction for the third competition is deferred "for a probationary period of five years."
Fenerbahce finished second in the Turkish league last season and was set to enter the Champions League at the third qualifying-round stage, needing to beat two opponents to enter the lucrative 32-team group stage.
The club was banished from the 2011-12 Champions League after the initial fixing allegations were made.
Besiktas' punishment stemmed from charges of fixing relating to the 2011 Turkish Cup final, which it won on penalties over city rival Istanbul BB.
Besiktas had qualified for the Europa League by finishing third in the league last season.
"In relation to the individuals of the clubs involved in the cases of Fenerbahçe and Besiktas, the CDB (UEFA Control and Disciplinary Body) decided that certain additional information will be collected in order to consider in further detail the different position of each of the individuals concerned," UEFA said.
Fenerbahce has identified five officials as being involved in its case - club president Aziz Yildirim, plus Alaeddin Yildirim, Sekip Mosturoglu, Ilhan Yuksel Eskioglu and Cemil Turhan.
In a third case, Steaua Bucharest - the 1986 European Cup winner - was banned from the next UEFA competition it qualified for, with the sanction deferred for a probationary period of five years. Its president Gigi Becali was convicted last month of attempting to pay bribes to influence a team to beat one of the club's title rivals in 2008.