Italy's prime minister told people to "stay at home" as the government limited travel and banned public gatherings across the whole country to combat the threat posed by the new coronavirus.
From Tuesday, the unprecedented quarantine measures will be extended from several large areas of the north to Italy's entire population of more than 60 million, according to a new decree signed on Monday night.
Since the COVID-19 disease first emerged in China late last year, Italy has become Europe's hardest-hit country and has seen a rapid rise in cases to more than 9,000 with 463 deaths reported so far.
The strict new rules, in place until April 3, also cancel sporting events "of all levels and disciplines", stopping play in the top-flight Serie A football league.
Only competitions organised by international bodies will be allowed to go ahead, but without spectators.
Before signing the decree, Prime Minister Giuseppe Conte said in a dramatic evening television address that it could "be summarised as follows: I stay at home". "Travel must be avoided across the entire peninsula unless it is justified by professional reasons, by cases of need or for health reasons," he told Italians.
The measures extend a quarantine zone that Italy had imposed for its industrial northern heartland around the cities of Milan and Venice on Sunday.
An AFP count showed Italy had recorded more than half of the 862 deaths reported outside China as of March 9 night.
'Moment of responsibility'
The national restrictions mean that schools and universities will all immediately close.
However, it was not immediately clear how all these measures would be enforced.
Trains and numerous flights continued to operate into and out of Milan on Monday despite the earlier set of restrictions for its Lombardy region. The government's first set of restrictions for Italy's north sent the stock market into a tailspin that saw the Milan exchange lose more than 11 percent on the day.
But the expansion of the northern restrictions to the rest of the country just a day later suggests a government struggling to cope with the scale of the medical emergency on its hands.
Italian health officials had warned on Saturday that the northern Lombardy region was starting to run out of hospital beds for its intensive care patients.
The government also began to recall retired doctors as part of an effort to quickly bolster the health service with 20,000 staff.
But the toll has kept growing by the day.
Italy recorded a record 133 deaths on Sunday and immediately announced that it was ordering 22 million surgical masks — even though doctors question how effective they are in halting the spread of viral infections.
The government's latest set of measures mean that people will need to fill out a standard "self-certification" form justifying their reasons for travel.
These would be submitted to the authorities at train stations and airports as well as major roads running between cities.
The government decree says its forms will work on an honours system and no proof of "need" will be required.
"Everyone must give up something to protect the health of citizens," said Conte.
"Today is our moment of responsibility. We cannot let our guard down."