The southern Italian region of Campania, which includes Naples, made it obligatory from Thursday to wear masks in public in order to stem a resurgence in coronavirus cases.
The regional president of Campania, Vincenzo De Luca, said the rule would remain in force until October 4.
It comes as Italy logged 1,640 new cases of the novel coronavirus in the past 24 hours, with Campania reporting 248, the highest of any region.
European health authorities have warned of a second wave of the novel coronavirus, as new infections have been rising since July.
“Responsible behaviour must be restored immediately, all the more so with the opening of schools,” said De Luca.
“If we want to avoid generalised closures, the maximum rigour is necessary.”
On Wednesday, the city of Genoa in Italy’s north also made masks obligatory in the historic centre, where crowds are more likely to gather.
Currently in Italy, masks must be worn inside shops and between 6pm and 6am (1600-0400 GMT) in crowded public areas.
Nearly 36,000 people have died from coronavirus in Italy and 302,537 have been infected.