The U.S. Geological Survey said the epicenter was about 25 miles north of Bologna, about 6 miles deep.
Some buildings collapsed when the ground shook for about 20 seconds in the Emilia region around 4 a.m., the Agenzia Giornalistica Italia reported.
A ceramics plant in Ferrara collapsed, killing one man working inside. Firefighters rescued other workers trapped in the rubble, AGI said.
"Churches and bell towers have been damaged," the report said.
Two of the other known fatalities suffered fatal heart attacks, La Repubblica reported.
The newspaper said the most serious damage occurred in the provinces of Modena and Ferrara, where many historic buildings collapsed. One regional official said he would be seeking a declaration of a national emergency to help displaced people.
Many took shelter in municipal buildings and schools, the newspaper said.
Rescue officials said they expect to find more casualties in the mountainous region, CNN reported.