Luca Zaia, governor of Veneto, said that coronavirus was “the absolutely worst problem” the region has faced during his career.
“As of this evening, there will be a ban on the Venice Carnival as well as on all events, including sporting ones, until 1 March inclusive,” he said.
It came hours after prime minister Giuseppe Conte authorised “emergency” measures in a bid to halt the spread of the ilness.
Until Friday, Italy had confirmed only three cases – all of them involving people who had recently arrived from the Chinese city of Wuhan.
By Sunday the number of cases in Lombardy had risen to 90, with a further 25 in Veneto and other isolated cases in the neighbouring regions of Piedmont and Emilia Romagna.
Two of the three Italian citizens who have died of coronavirus within the last 48 hours are believed to be a 78-year-old man in Veneto and a 77-year-old woman in Lombardy. Details about the third victim, whose death was confirmed late on Sunday, have not yet been released.
However health officials say they have not yet traced the source of the outbreak. ”We are even more worried because if we cannot find ‘patient zero’ then it means the virus is even more ubiquitous than we thought,” said Mr Zaia.
Towns in Veneto and Lombardy with a combined population of 50,000 have effectively been placed under quarantine after officials urged the public to stay home.
Mr Conte said nobody would be permitted to enter or leave the areas without special permission but rejected calls to reintroduce border controls to prevent new arrivals into the country.
The municipalities on effective lockdown include Casalpusterlengo, Codogno, Castiglione d’Adda, Fombio, Maleo, Somaglia, Bertonico, Terranova dei Passerini, Castelgerundo and San Fiorano, although observers said police did not appear to be stopping cars entering or leaving.
Three Serie A soccer matches due to take place on Sunday were postponed amid a cancellation of all sporting events in the affected provinces.
Bishops in several dioceses in northern Italy issued directives that holy water fonts be kept empty and that priests place communion wafers in the hands of the faithful rather than their mouths during mass.
Worshippers have been urged to refrain from shaking hands or exchanging kisses during the sign of peace ritual.
Archbishop Rino Fisichella, a Vatican official whose family live in Codogno, said it was “obvious that we need to use all necessary prudence” to prevent the spread of the virus.
Additional reporting by agencies