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 25 and have also been fined 30,000 euros.
UEFA said 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 on Dec. 10.
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 ultras when they host Borussia Dortmund, also on Feb. 25.
UEFA said 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".
- Sports & Recreation
- Manchester United