Their faces masked by a long banner reading “Honour to Benito Mussolini”, the group sang Fascist songs and performed the Nazi salute near the city's Piazza Loreto, where the defeated dictator's body was strung up in 1945, the Gazzetta dello Sport reported.
A short video circulating on social media shows the group holding up the banner, signed 'IRR' in a reference to the Irriducibili — Lazio's hardcore 'ultra' supporters who have a long history of hard-right politics.
Around 50 members of the Lazio ultra group Irriducibili in Milan city centre holding a sign which reads: 'Hail Mussolini' pic.twitter.com/A5wU6vlmJ6
— Andrew Cesare (@AndrewCesare) April 24, 2019
The flash mob came a day before Italy's Liberation Day, celebrating the end of Nazi occupation, and ahead of a match in Milan already marked by tension between the two teams.
READ ALSO: What is Italy's Liberation Day all about?
The Serie A clash between them at the San Siro earlier this month finished with Milan 1-0 winners and scuffles on the pitch after the home players held up the shirt of Lazio player Francesco Acerbi to their own fans like a trophy. Milan midfielders Tiemoue Bakayoko and Franck Kessie were fined a total of €86,000 for the incident.
Photo: Miguel Medina/AFP
Meanwhile, a video of racist chants directed at Frenchman Bakayoko by a group of Lazio fans also circulated on social media.
Milan's mayor Giuseppe Sala said the police were investigating Wednesday's flash mob and insisted the northern Italian metropolis “is and will remain forever a profoundly anti-fascist city”.
In Italy “apology for fascism” is a crime, but some cases have been thrown out in recent years on freedom of speech grounds.