A magnitude 6.0 earthquake shook Italy's historic northeast city of Ferrara.
The 6.0-magnitude quake struck around 0200 GMT, sending thousands of people running into the streets in town and cities from the Emilia-Romagna region to Venice.
The quake's epicentre was the commune of Finale Emilia, 36 kilometers (22 miles) north of Bologna.
A powerful earthquake shook Italy's industrial and densely populated northeast early Sunday, killing six people and felling homes and church steeples around the historic city of Ferrara.
Emergency services said at least 50 people were injured in the 6.0-magnitude quake, which struck just after 4 a.m. (10 p.m. ET Saturday), sending thousands of people running into the streets in town and cities from the Emilia-Romagna region to Venice.
Authorities said the quake's epicenter was the commune of Finale Emilia, 36 kilometers (22 miles) north of Bologna.
A 29-year-old Moroccan man was killed by a falling girder when a factory building collapsed in the small town of Ponte Rodoni di Bondeno.
Two Italian workers died when a roof caved in at a ceramics factory in Sant-Agostino. And another worker was reported missing when the roof of another factory collapsed in a town in the same area.
One of the men killed in the factory collapse, Nicola Cavicchi, 35, "wanted to go to the seaside but because of the bad weather forecast he decided to go to work to replace a colleague who was sick," a family member told local media.
Another worker was reported missing in the collapse of a roof on a foundry in another village in the same area.
And a 37-year-old women died near Bologna, with reports suggesting she may have had a heart attack brought on by panic during the quake.
In Finale Emilia, firefighters rescued a five-year-old girl who was trapped in the rubble of her house after a rapid series of phone calls between a local woman, a family friend who was in New York and emergency services.
The magnitude 6.0 quake happened at a depth of 5.1 kilometers (3.2 miles) and lasted around 20 seconds, followed by several aftershocks.
"We were very afraid, all the village went out into the street after the first shock, after the second many took shelter in their cars, but fortunately the damage was fairly limited, above all affecting churches," Umberto Mazza, the mayor of Ostiglia, near Mantua, told the Italian news agency ANSA.
First television footage showed half-collapsed houses with heaps of rubble on the roads. Several church steeples and towers also partly collapsed.
The region shaken by the quake is Italy's industrial heartland but also home to priceless architectural and art treasures. The historic center of Ferrara is classified as a world heritage site.
Hospitals were evacuated as a precautionary measure.
Telephone switchboards of emergency services were inundated with calls immediately after the quake.
Earlier a 4.1-magnitude quake shook the Lombardy region around Milan, Italy's financial and business capital, and was felt in the historic cities of Modena, Mantua and Rovigo as well as Ferrara.
Seismic experts said the relatively small size of the aftershocks meant the worst was likely over.
In a show of calm nerves, officials opened polls as planned for the second round of local elections in the cities of Piacenza, Parma, Budrio and Comacchio.
Enzo Boschi, a reputed seismologist in Italy, said: "It is not true that there are never earthquakes in the Po plain. Ferrara suffered a very big one in the 15th century. You can still see the traces."
"Italy is a very quake-prone country. What we can say is that 5.9 or 6.0 is the maximum strength there has ever been in these zones in the past."
In March 2009, a 6.3 magnitude quake devastated the central city of l'Aquila, killing some 300 people and leaving tens of thousands homeless.