ROME (Reuters) - Italy’s southern regions warned hundreds of thousands of its people who emigrated to the wealthy north of the country not to return home, amid fears of an exodus from a no-go zone set up to halt an outbreak of coronavirus.

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The unprecedented lockdown was announced by the government overnight and will affect some 16 million inhabitants in the region of Lombardy, which is centered on the financial capital Milan, and 14 prosperous provinces also in the north.

An estimated two million people have left the underdeveloped south in the past 15 years in search of work and hundreds of thousands of them have settled in the north. With a four-week shutdown looming, many of them are expected to try to return to their old family homes to sit out the contagion.

However, the governor of Puglia, the heel of Italy’s boot, made an impassioned plea on Facebook for them to remain in the north, the epicenter of Europe’s worst coronavirus outbreak.

“I speak to you as if you were my children, my brothers, my nephews and nieces: stop and go back,” said Michele Emiliano. “Get off at the first train station, do not catch planes ... turn your cars around, get off your buses. Do not bring the Lombard, Veneto and Emilia epidemic to Puglia.”

The northern regions of Lombardy, Emilia-Romagna and Veneto represent 85% of all the 5,883 confirmed cases to date and 92% of the 233 recorded deaths. By contrast, the southern regions of Puglia, Basilicata, Calabria, Campania and Molise have between them had barely 100 cases and just two deaths.

Looking to deter a mass influx, all five regions issued decrees on Sunday saying people arriving from the northern red zones had to go into self-imposed quarantine for two weeks.

“The government must block an exodus to Calabria, which risks triggering a disastrous bomb,” said Jole Santelli, the president of Calabria, the impoverished toe of Italy.

“Calabria is not in a position to manage a serious health emergency .... Returning from the north in an uncontrolled manner endangers our land and our loved ones. Don’t do it. Stop.”

The government appears to be giving people a day before formally enacting the lockdown and television showed hundreds of travelers flowing into Milan’s central station overnight to catch trains out of the city.

Airports and roads were also all open.