A security official in Kano city confirmed to the BBC that the engineer was fatally shot, although details about the death weren't immediately known. Residents said they heard gunfire during the morning.
In March, a video purportedly from al-Qaida's north African affiliate demanded that Germany free a woman jailed on terror charges in exchange for the engineer's release.
The Italian engineer abducted Monday in Kwara state works for Borini Prono, an Italian building and civil engineering firm, officials said. "We are in contact with the authorities and the Italian embassy in Nigeria and we are following developments with apprehension," a company spokesperson said.
A Nigerian government spokesman said the man was kidnapped while at a work site in Ilorin, Kwara's capital.
The Italian news agency ANSA said Nigeria media reported the kidnappers haven't contacted authorities.