The death of coronavirus patients in Italy shot up from 233 to 366 on Sunday, officials reported.
Italy on Saturday 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 on Saturday, Italy's civil protection agency said the number of people with the coronavirus rose by 1,247 in the past 24 hours, taking the total to 5,883.
Another 36 people also died as a result of the virus, taking the total to 233 on Saturday.
There was chaos and confusion in the northern Italian city of Padua in the Veneto region as word spread late Saturday evening that the government was planning to announce the quarantine.
Northern Italy in quarantine
Italy's prime minister announced a sweeping coronavirus quarantine early Sunday, restricting the movements of about a quarter of the country's population in a bid to limit contagions at the epicentre of Europe's outbreak.
Shortly after midnight, Prime Minister Giuseppe Conte signed a decree affecting about 16 million people in the country's prosperous north, including the Lombardy region and at least 15 provinces in neighbouring regions.
The extraordinary measures will be in place until April 3.
"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," Conte said.