The two Italians worked for construction company Impregilo, an Italian Foreign Ministry spokesman in Rome said.
Following their kidnapping, the Italian foreign minister recommended that all Italians leave the Niger Delta area.
Rising violence against foreigners in the world's sixth largest oil exporter has prompted thousands of oil workers to leave the delta and oil exports are down by a fifth.
Two foreign workers, a Dutch and a Belgian, were killed in January, an unusually high toll for one month.
A US oil executive was shot dead in his car in Port Harcourt last May.
The abduction of the Italians means that 10 foreigners are being held by different armed groups in the delta, a vast maze of mangrove-lined creeks and swamps.
A Lebanese hostage regained his freedom on Wednesday after spending 11 weeks in captivity.
The man's employer, Italian oil giant ENI, said he was released, but the group holding him said he escaped and vowed revenge on the company and state government.
That group, the Movement for the Emancipation of the Niger Delta (MEND), denied any involvement in Friday's killing however.
MEND has the highest profile among a number of groups operating in the Niger delta who are seeking to highlight imbalances in the distribution of oil wealth in the region.
The incidents come as at least seven people were killed in two days of communal clashes in a villages close to Port Harcourt.