Travel was restricted across Italy from Tuesday and public gatherings were forbidden throughout the country, as the government placed the whole peninsula on lockdown to fight the spread of the new coronavirus.
Marriages and funerals were banned for more than three weeks under the quarantine and bars and restaurants were told to close at 6pm, with the prime minister urging people to "stay at home".
The unprecedented measures, in place until April 3, were extended from several large areas of the north to Italy's entire population of more than 60 million in a decree signed 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 more than 400 deaths so far.
"All forms of gatherings in public places or sites open to the public" were banned, the decree said, while sporting events of all levels and disciplines were cancelled -- stopping play in the top-flight Serie A football league.
Under the new rules travel is only allowed for the most urgent work or health reasons, but people will be able to return to their own homes from elsewhere.
The measures extend a quarantine zone that Italy had imposed for its industrial northern heartland around the cities of Milan and Venice on Sunday.
Schools and universities were all immediately closed and businesses were urged to give their employees leave.
Bars and restaurants were only allowed to open between 6am and 6pm, the decree said, and only if a distance of at least a metre was possible between customers.
Religious institutions will also stay open as long as people can keep the same distance from each other -- but ceremonies such as marriages, baptisms and funerals are banned until April 3.
As of Monday night, an AFP count showed Italy had recorded more than half of the deaths reported outside China.
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".
"Everyone must give up something to protect the health of citizens," he said.
"Today is our moment of responsibility. We cannot let our guard down."
However, it was not immediately clear how all the new 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.
People who wish to go to another part of the country will be required to fill out a standardised form justifying their reasons for travel.
The government decree said these forms, to be submitted to authorities at train stations and airports, as well as at major roads between cities, will work on an honour system and no proof of "need" will be required.
Supermarkets open overnight in Rome and Naples were packed with residents stocking up on food as well as soap and disinfectant, Italian media reported.
Images showed people waiting calmly in queues outside the shops in the middle of the night, despite the government decree assuring that supermarkets will still be regularly restocked and asking Italians not to "go mad" with panic buying.
All ski resorts were out of action and cinemas, museums, nightclubs and similar venues must remain shut after being ordered to close their doors over the weekend, the decree said.
Only sports competitions organised by international bodies will be allowed to go ahead -- but without spectators.
Italian officials faced a further headache after prisoners fearful of infection protested or rioted in 23 jails across the country -- leaving several dead.
Some prisoners have been asking to be granted amnesty over the health crisis.
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 the government is struggling to cope with the scale of the medical emergency.
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.