Italians still held
A diplomatic source in Nigeria said Moro and Passarin were freed on a road outside Port Harcourt, the nation's oil capital.
The men were abducted last Friday after gunmen stormed into the Impregilo offices, about 40km from Port Harcourt.
The kidnappings led to a call from the Italian foreign ministry to all Italian companies operating in the Niger Delta to withdraw expatriate staff.
Two other Italians working for Italian oil giant Agip abducted on December 7 are still being held by the separatist group the Movement for the Emancipation of the Niger Delta.
The Italian foreign ministry said it did not believe the group was involved in last Friday's abductions.
Over the past year, more than 100 foreign workers have been kidnapped in the Niger Delta.