Olympiakos was fined 90,000 euros following crowd trouble in its Europa League match against AC Milan last month.
UEFA sanctioned the Greek side on Friday over a pitch invasion, the setting-off of fireworks and blocked stairways during its 3-1 win over Milan on December 13 in Piraeus.
Olympiakos must play its next home match behind closed doors although this was deferred for a “probationary period” of two years. The Reds face Dinamo Kiev for the Round of 32 next month.
Milan coach Gennaro Gattuso suggested that Olympiakos threw extra balls onto the pitch and mentioned a “strange trumpet noise”, although he said it was not an excuse for the Italians’ defeat.
Milan was fined 5,000 euros after its fans also set off fireworks.