Police arrested approximately 20 people during an unauthorized protest late Friday after about 200 people gathered in the city centre were stopped from entering the Renaissance city's Piazza della Signorina, newspapers reported.
Clashes broke out in neighboring streets with police in riot gear, with some protesters hurling Molotov cocktails, bottles and rocks at authorities, overturning trash bins and breaking security cameras.
"We've lived a surreal, terrible and painful night in Florence," wrote Florence Mayor Dario Nardella on Facebook early on Saturday, AFP reported.
"This is not how you protest your grievances, this is not how you voice your suffering," Nardella wrote. "It's only violence as an end in itself, gratuitous.
"Those who scar Florence must pay for what they have done."
In Bologna, a few hundred people also protested, most of them young men, including football hooligans and some giving the Fascist salute, La Repubblica daily reported.
Video images showed the newspaper's video journalist being harassed and chased away.
"Journalist, terrorist!" shouted the crowd.
Protesters have taken to the streets in the past week in various cities across Italy to criticize a new series of measures to stop rising coronavirus cases in the country.
Italy reported over 31,084 new cases of the virus on Friday, breaking a new daily record.
Last Sunday, Prime Minister Giuseppe Conte brought in new nationwide coronavirus restrictions, including the closure of all cinemas, theatres, gyms and swimming pools and the closing of restaurants at 6pm.
Conte has said he wants to give the latest measures two weeks to take effect before deciding whether a fuller lockdown is needed, as has been ordered in France.
The government has announced that five billion euros (S$7.97 billion) will be issued to the worst-hit professions, including restaurants, taxi drivers and live entertainment venues.
The new measures spurred a wave of demonstrations in Rome, Milan, Naples and Turin on Monday and Tuesday, marked by violence and vandalism, with riot police firing teargas at groups of young people hurling bottles and rocks.