Italy is now split into three zones: red for high risk, then orange and yellow. The red areas are Lombardy, Piedmont and Aosta Valley in the north and Calabria in the south.
The whole country has a night curfew.
In neighbouring Slovenia police clashed with violent anti-lockdown protesters.
Riot police used water cannon and teargas to disperse the crowd of several hundred outside parliament in the capital Ljubljana. Some demonstrators threw bottles, stones and smoke bombs at officers.
Slovenia is under partial lockdown, as coronavirus infections have spiked there as in much of Europe. Thursday night's violence was the worst in Slovenia for years.
In Italy's red zones, which cover an estimated 16.5 million people in a population of 60 million, you can now only leave home for work, health reasons, essential shopping or emergencies, but all non-essential shops are closed.
Bars and restaurants are also shut but people can exercise near their homes if they wear masks and hairdressers can remain open.
Lombardy, which includes Milan, was the worst-hit area in Italy's March crisis - and it was Europe's first coronavirus hotspot.
Nationally all older secondary school pupils in Italy are studying from home.
The orange - medium-risk - regions are Puglia and Sicily in the south. People there can move freely but not leave their home town or city, and shops remain open. In the yellow zone, including Rome, only the national restrictions apply, which involve a curfew from 22:00 to 05:00 local time.