Italy's governing Democratic Party have led a rally to warn about fascism making a comeback in the nation, which had suffered under fascist dictator Benito Mussolini.

Several thousand people turned out in Como, northern Italy, where right-wing extremists recently interrupted an NGO meeting about migrants' housing. Earlier this week, a neo-fascist party attacked a liberal newspaper's Rome office.

The post-war Italian Constitution, adopted a few years after Mussolini's regime's demise, outlaws any return of fascist organisations.

Citing the constitution, Chamber of Deputies President Laura Boldrini said at the rally it was the "duty of all democratic forces, of civil society, of citizens" to show opposition to fascism.

Shunning the rally was the populist opposition 5-Star Movement, which recent opinion polls peg as Italy's No. 1 party before the 2018 election. Deputy 5SM leader Angelo Tofalo sparked outrage in Italy when he finished a speech by shouting "Boia Chi Molla (He Who Abandons The Fight Is A Killer)", a notorious fascist slogan.