The victims include four people from the same family who were found dead in a flooded house in the Tuscan city.
Authorities in the coastal city have accused the civil protection department and weather experts of sending warnings of the deadly floods too late.
Italian Premier Paolo Gentiloni urged all the institutions in Livorno to put aside their differences and focus on the community in the wake of the disaster.
“To the victims go not only our thoughts but also the solidarity of the whole country,” Gentiloni added.
Livorno Mayor Filippo Nogarin said that the city’s authorities were working non-stop to assist residents following the disaster.
“The city is trying to raise its head again with great labour and pain,” he added.
“The civil protection department, the fire brigade, the technicians of [environmental services company] ASA and [power group] ENEL are doing an extraordinary job together with the volunteers, and we can see the results.”
Several areas in Rome were also flooded causing various metro stations to close temporarily.
The storm front has now moved further south causing floods in and around Salerno, while mud and rocks have engulfed basements in and around Avellino.
Storms have also battered Palermo and Catania, where strong gusts have uprooted trees and caused chaos in the Sicilian cities.