Some supporters of Lazio hung a banner honouring Benito Mussolini and chanted racial abuse at AC Milan's Tiemoue Bakayoko ahead of Wednesday night's Coppa Italia match.
The two teams met at San Siro for the second leg of their cup semi-final, and the atmosphere turned ugly in Milan prior to kick-off.
A group of Lazio ultras unveiled a banner that read "Honour to Benito Mussolini" and performed fascist salutes near the Piazzale Loreto, the Milan square where the fascist dictator was executed in 1945.
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The displays took place just one day before an Italian national holiday in which the country celebrates the end of Nazi-fascism.