Statements from the two countries confirm the killings announced on Saturday.
A statement from Italy’s foreign ministry, called the killings “atrocious act of terrorism”.
“It’s an atrocious act of terrorism, against which the Italian government expresses its firmest condemnation, and which has no explanation, if not that of barbarous and blind violence,” the statement read.
Another statement from the Greece’s foreign ministry said “We note that the terrorists never communicated or formulated demands to release the hostages.”
Both countries deny claims by Ansaru that they carried out the killings because of an attempt by Nigerian and British security forces.
Nigeria has yet to comment on the killings.
Britain had earlier on Sunday denied taking part in any rescue operations that may have necessitated Ansaru’ action, as the group claims.
Britain said its military planes, sighted in Abuja, were meant to convey Nigerian troops to Mali, and were never meant for a rescue mission in Bauchi or anywhere else where the captives were held.
Breakaway extremist group, Ansaru, said Saturday it killed the seven foreign construction worker abducted in Bauchi state a fortnight ago in an online message.
The message said the workers were killed because of attempt by Nigeria and Britain to free them. The statement, published on Islamist website, contains shots purporting to show the killing.
“(We) announced the capture of seven Christian foreigners and warned that should there be any attempt by force to rescue them will render their lives in danger,” the statement said.
“The Nigeria and British government operation lead to the death of all the seven Christian foreigners. As a result of this operation, the seven hostages were killed,” the group said in the statement.
It said a video of the killings would be posted online.
Gunmen killed a security guard on February 16 before abducting the men in Setraco compound in Jama’are, Bauchi. Ansaru later claimed they were attacked because of France’s military intervention in Mali.
Those kidnapped include citizens of Britain, Greece, Lebanon and Italy.