More than a quarter of Italy's population have been placed in mandatory quarantine as the government attempts to stem the spread of the coronavirus.
Prime Minister Giuseppe Conte signed a decree just after midnight, which affects about 16 million people in the country's prosperous north, including the Lombardy region and at least 14 provinces in neighbouring regions.
The measures will be in place until April 3.
Mr Conte said: "For Lombardy and for the other northern provinces that I have listed there will be a ban for everybody to move in and out of these territories and also within the same territory.
"Exceptions will be allowed only for proven professional needs, exceptional cases and health issues."
Around the world, more and more countries are bracing for a surge in virus cases.
Western countries have been increasingly imitating China – where the virus first emerged late last year, and which has suffered the vast majority of infections – by imposing travel controls and shutting down public events.
On Saturday, Italy saw its biggest daily increase in coronavirus cases since the outbreak began in the north of the country on February 21.
In its daily update, Italy's civil protection agency said the number of people with the coronavirus rose by 1,247 in the last 24 hours, taking the total to 5,883. Another 36 people also died as a result of the virus, taking the total to 233.
There was chaos and confusion hours before Mr Conte signed the decree, as word spread that the government was planning the quarantine.
Packed bars and restaurants emptied quickly as people rushed to the railway station in Padua's Veneto region. Travellers with suitcases, wearing face masks, gloves and carrying bottles of sanitising gel shoved their way on to trains.
Some regional politicians were also taken by surprise.
Stefano Bonaccini, president of the Emilia Romagna region, said parts of the decree were confusing, and asked the premier for more time to come up with "coherent" solutions.
The mayor of Asti, in the Piedmont region, posted an irate video on his Facebook page condemning Rome for not keeping regional leaders in the loop.
"Nobody told me," said Maurizio Rasero, adding that he had hundreds of messages on his mobile phone from alarmed citizens. "It's incredible that information that is so delicate and important would come out in the newspaper first, leaking everywhere even before local authorities learn about it."
Other countries around the world were also limiting activities, with events and festivals called off, and travel restrictions and warnings issued.
A nosedive in tourist traffic and possible disruptions to supply chains sparked fears of a worldwide economic slowdown.
Saudi Arabia banned spectators at any sports competitions, and the NBA, as well as British and Japanese sports teams, are considering doing the same, as baseball and soccer seasons are starting.
The spread of the virus has also taken a psychological toll.
Authorities and manufacturers have been trying to assure panicking consumers they do not need to hoard toilet paper, which has vanished from store shelves in various nations.
Of particular concern are passenger-packed cruise ships, many of which are confronting their own virus problems.
The Grand Princess, where 21 people tested positive for the virus, was heading for the port of Oakland, California, after idling off San Francisco for several days. There is evidence that the ship was the breeding ground for a deadly cluster of almost 20 cases during an earlier voyage.
"Those that will need to be quarantined will be quarantined," US Vice President Mike Pence said. "Those who will require medical help will receive it."
President Donald Trump said he would have preferred not to let the passengers disembark on to American soil, but would defer to medical experts.
In Egypt, a cruise ship on the Nile with more than 150 people on board was under quarantine in the southern city of Luxor after 12 positive tests.
Also on Saturday, the port of Penang in Malaysia turned away the cruise ship Costa Fortuna because 64 of the 2,000 on board are from Italy. The ship had already been rejected by Thailand, and is now heading to Singapore.
And in Malta, which reported its first case of the virus on Saturday, the MSC Opera ship agreed not to enter the Mediterranean country's port amid local worries – even though there are no infections suspected on board. The ship continued to Messina, Sicily, where passengers were allowed to disembark after officials reviewed medical records.
While the global death toll has risen past 3,400, more people have now recovered from the virus than are ill with it.
As of Saturday, nearly 90,000 cases have been reported in Asia; more than 8,000 in Europe; 6,000 in the Middle East; about 450 in North America, Latin America and the Caribbean; and fewer than 50 cases reported so far in Africa.
As of today's reports, global number of #COVID19 confirmed cases has surpassed 100K.WHO reminds all countries & communities that the spread of this #coronavirus can be significantly slowed or even reversed through robust containment & control activities https://t.co/7jTx7fJyIwpic.twitter.com/fLxLDOtxCH
— World Health Organization (WHO) (@WHO) March 7, 2020
While many scientists said the world is clearly in the grip of a pandemic – a serious global outbreak – the World Health Organisation isn't calling it that yet, saying the word might spook the world further.
The virus is still much less widespread than annual flu epidemics, which cause up to five million severe cases around the world and up to 650,000 deaths annually, according to the WHO.
In Iran, fears over the virus and the government's waning credibility has become a major challenge to leaders already reeling from American sanctions. More than 1,000 infections were confirmed overnight, taking the country's total to 5,823 cases, including 145 deaths.
South Korea, the hardest-hit country outside China, reported 93 new cases on Sunday morning, taking the total to 7,134, with 50 deaths overall.
China on Sunday morning reported 44 new cases over the past 24 hours, the lowest level since it began publishing nationwide figures on January 20, and 27 new deaths.
But while infections were increasing more slowly, the country was struck by a fresh tragedy: A hotel used for medical observation of people who had contact with coronavirus patients collapsed on Saturday, killing at least four people.
In the United States, the US Centres for Disease Control and Prevention urged older adults and people with severe medical conditions to "stay home as much as possible" and avoid crowds.
The number of deaths linked to coronavirus in Washington state reached 16, although that figure could be higher, based on figures released by the nursing home at the centre of the outbreak.
The Life Care Centre of Kirkland said on Saturday that, since February 19, 26 of its residents have died. Typically, about three to seven residents die at the facility each month.
Even islands in the middle of the Indian Ocean have not been spared, with the tiny archipelago nation of the Maldives reporting its first cases. Health authorities there locked down two of its tourist resorts after two expatriate workers tested positive for the coronavirus.