UEFA has punished Steaua Bucharest, Debrecen and Maribor for racist behaviour by their fans at Champions League matches last month.
The three clubs have been told that they must close sections at their stadiums for the next Champions League or Europa League match that they host.
Steaua's sanction will happen on Wednesday when two sections of the National Arena will be shut against Kazakhstan champions Aktobe in their Champions League third qualifying round, second-leg match.
UEFA's disciplinary panel acted on reports of racist incidents when Steaua beat Norway's Stromsgodset 2-0 on July 23.
Debrecen of Hungary must shut sector B of its ground after fans showed an "illicit banner" during a match against Northern Ireland team Cliftonville.
Slovenia's Maribor will close the 'Jug' section of its stadium following racist behaviour when Zrinjski of Bosnia-Herzegovina visited.
"The fight against racism is a high priority for UEFA," said a statement on UEFA's website.
"The European governing body has a zero-tolerance policy towards racism and discrimination on the pitch and in the stands."