Raggi opposes Forza Nuova plan to commemorate Mussolini march.
A planned demonstration in central Rome by far-right political party Forza Nuova (FN) faces opposition from the city's mayor Virginia Raggi as well as Rome members of the centre-left Partito Democratico.
Italy's interior minister Marco Minniti is under pressure to ban the demonstration which is planned for 28 October. The FN chose this date to commemorate the 95th anniversary of Mussolini's March on Rome, in 1922, which marked the beginning of fascist rule in Italy.
Mayor Raggi tweeted "the #MarchOnRome cannot and must not be repeated" while the PD say the proposed event "risks turning into a tragic day for our country".
However FN leader Roberto Fiore described the planned march as "a patriotic demonstration, not pro-fascist or nostalgic," warning that the interior ministry would be wrong to ban the event.
The controversy follows a decision by Rome police chief Guido Marino to ban the FN from staging a so-called "security walk" in the capital's Tiburtino III neighbourhood on the evening of 8 September, the anniversary of the day when Italy signed the armistice with the Allied forces in 1943 and abandoned Rome to the German forces. The Tiburtino III area was the scene of recent clashes between locals and residents of a migrant centre during which an Eritrean man was stabbed in the back.