MILAN—The Italian government is locking down 17 million people—more than a quarter of its population—including in Milan, the surrounding Lombardy region and 14 neighboring provinces, in the most sweeping steps any European country has prepared to take against the coronavirus epidemic.

A decree from the Italian Prime Minister’s office says people living in Lombardy, where Milan is the capital, and the named provinces in Lombardy’s nearby regions must “absolutely avoid any movement into and out of the areas.”

Police, emergency services and if needed the army will be available to enforce the quarantine. People violating the lockdown can be punished with a fine or jail terms, according to the draft decree.

Prime Minister Giuseppe Conte announced the measures in a press conference in the early hours of Sunday morning. He said the final decree would be published “in the coming hours.”

The quarantine will be effective from Sunday until April 3.