UEFA has ordered Olympiakos and Zenit St Petersburg to play their Champions League last-16 home games in partially closed stadiums after racist behaviour by fans during games earlier in the competition.
Olympiakos, who face Manchester United at the Karaiskakis Stadium in the last-16 first leg on Feb. 25, must close the lower tier of the north stand and have also been fined 30,000 euros.
UEFA said the sanctions had been imposed on Olympiakos for "the racist conduct of supporters, insufficient organisation, the setting-off of fireworks and the use of a laser" during the club’s 3-1 group-stage win on Dec. 10.
A statement from European football's governing body added: "There will be a partial closure of the Greek club's stadium -- the lower tier of the north stand -- for their next UEFA competition home match. They have also been fined 30,000 euros."
Zenit, meanwhile, will have to close the section of the Petrovsky Stadium where the club’s ultras are located for their last-16 first leg against Borussia Dortmund 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" during their 4-1 defeat at Austria Vienna on Dec. 11.
Both clubs have the right to lodge an appeal against the decisions.