Italy has placed up to 16 million people under quarantine as it battles to contain the spread of coronavirus.
Anyone living in Lombardy and 14 other central and northern provinces will need special permission to travel. Milan and Venice are both affected.
Schools, gyms, pools, and ski resorts will be closed and all events in “public and private spaces” suspended, Prime Minister Giuseppe Conte said.
The drastic measures will last until 3 April.
Last week the government announced the closure of all schools and universities across the country for 10 days.
Italy has seen the largest number of coronavirus cases in Europe and reported a steep rise in infections on Saturday.
The death toll in Italy has passed 230, with officials reporting more than 36 deaths in 24 hours. The number of confirmed cases jumped by more than 1,200 to 5,883 on Saturday.
“We want to guarantee the health of our citizens. We understand that these measures will impose sacrifices, sometimes small and sometimes very big,” Mr Conte said early on Sunday.
“But this is a time where we must take responsibility for ourselves.”
Under the new measures, people will be unable to enter or leave the whole northern region of Lombardy, home to 10 million people, except for emergency access. Milan is the main city in the region.
Mr Conte said the 14 provinces affected were Modena, Parma, Piacenza, Reggio Emilia, Rimini, Pesaro and Urbino, Alessandria, Asti, Novara, Verbano Cusio Ossola, Vercelli, Padua, Treviso and Venice.
Until now only around 50,000 people in northern Italy had been affected by quarantine measures.
What are the details?
Weddings and funerals have been suspended, as well as religious and cultural events. Cinemas, night clubs, gyms, swimming pools, museums and ski resorts have been closed.
Restaurants and cafes can open between 06:00 and 18:00 but customers must sit at least 1m (3ft) apart.
People have been told to stay at home as much as possible, and those who break the quarantine could face three months in jail.
Sports competitions will close to the public, and the president of Italy’s football players’ union has called for all matches to be postponed.
The World Health Organization (WHO) has advised Italy to focus on virus containment measures as infections spread in the country.
The plans echo China’s forced quarantine of millions of people which the WHO has praised for halting the spread of the virus.
Leading Italian politician Nicola Zingaretti said on Saturday he had tested positive for the virus.
“I am fine but I will have to stay home for the next few days,” the leader of Italy’s centre-left Democratic Party (PD) said in a Facebook post.
The country has said it will start recruiting retired doctors in an effort to combat the escalating outbreak.
