Olympiakos and Zenit St Petersburg will play their Champions League round of 16 home games in partially closed stadiums because of racist behaviour by their fans.
The Greek side will have to close the lower tier of the north stand of their stadium in the first leg match against Manchester United on February 25th and have also been fined 50 thousand dollars.
UEFA says the sanctions were imposed for "the racist conduct of supporters, insufficient organisation, the setting-off of fireworks and the use of a laser" during the group stage match at home to Anderlecht last week.
Zenit were sanctioned for incidents during their 4-1 defeat at Austria Vienna and will have to close the area of the stadium which usually houses their fiercest fans when they host Borussia Dortmund, also on February 25th.
UEFA says the Russian club had been punished for "the racist behaviour of fans - namely the displaying of a banner - the setting-off and throwing of fireworks and crowd disturbances".