Around 16 million Italians have been quarantined as the government introduced drastic measures to try to stop the rapid spread of coronavirus.
There was panic and confusion as the lockdown - across the entire Lombardy region and 14 provinces in four other regions - came into force after the number of people to test positive for COVID-19 increased by 1,247 in a single 24-hour period.
The total number of coronavirus cases in the country jumped to 5,883 - and a further 36 people also died, taking the total number of deaths to 233.
The unprecedented decree, that affects more than a quarter of Italians, forbids anyone from leaving or entering the new red zones except for exceptional circumstances until at least 3 April.
It applies to some 10 million residents in Lombardy - which includes the financial capital Milan - and another six million in the northern provinces of Modena, Parma, Piacenza, Reggio Emilia, Rimini, Pesaro, Urbino, Alessandria, Asti, Novara, Verbano-Cusio-Ossola, Vercelli, Padua, Treviso and the tourist hotspot of Venice.
The clampdown represents the most widespread effort outside of China - the origin of the deadly disease - to stop the spread of the coronavirus.