Italian President Giorgio Napolitano called the abortive British military operation "quite inexplicable" but the Italian media was more scathing. It accused Britain of imperialist arrogance and insensitive disregard for Italy, its EU partner and NATO ally.
Briton Chris McManus, 28,and Italian Franco Lamolinara died apparently during a rescue attempt Thursday by British and Nigerian forces in the northeastern city of Maiduguri, a stronghold of Muslim militants. Versions of events that led to the men's deaths have multiplied as the row deepened.
McManus and Lamolinara worked for Italian firm B. Stabilini in the construction of a local headquarters for the Central Bank of Nigeria. European presence is equated in the impoverished region with the federal government's and outside world's disregard for the largely Muslim community's woes.
Widespread deprivation has become a breeding ground for extreme militancy, led by Boko Haram Islamist militant group.
Although British Defense Secretary Philip Hammond said the operation was "completely explicable" it was increasingly clear a diplomatic row was brewing at the highest level, and the matter wouldn't go away.
A grim-faced British Prime Minister David Cameron announced the failed rescue but Italian analysts said the implications for Italy's precariously balanced coalition would be potentially damaging.
Italian Prime Minister Mario Monti is leading a coalition of technocrats tasked with rescuing Italian economy. A diplomatic embarrassment that highlights the government's inexperience with diplomacy and defense is the last thing Monti needs.
The Corriere della Serra newspaper said the episode had left Italy humiliated.
Both Cameron and Hammond said Italy was informed of the operation at the last moment but Italian analysts said the fact that Britain put together a rescue team and dispatched it to the suspected hideout meant it had taken much longer to put the operation together but not bothered to inform Italy.
Cameron's spokesman said, "We contacted the Italians yesterday (Thursday) as the operation was getting under way, but this was a very fast-moving situation.
"Our priority was to respond to the situation on the ground and to do everything we could to try and secure the safe release of the hostages."
An earlier Cameron statement announcing the operation and the deaths of McManus and Lamolinara also said the decision to act had been taken at very short notice.
Hammond told the BBC the attempted rescue was launched after information the captives "were about to be moved -- possibly executed."
What had subsequently happened was "very unfortunate but it's completely explicable," Hammond said.
"These hostages were taken, they were held at an unknown location for very a long period of time despite extensive efforts to track them down. And when a window of opportunity became available, a well-trained Nigerian force with British support went in and tried to rescue them," he said.
Hammond said Italy "was kept informed throughout the operation as the intelligence emerged and then as the decision was taken to act.
"I don't think they specifically approved it -- they were informed of what was happening."
Cameron's office said it had received no official complaint from Italy and the United Kingdom hadn't made an apology.
Napolitano's comments challenged the British version. The president said Britain needed to explain why it didn't inform the Italian authorities ahead of the operation.
"The way the British government has behaved is quite inexplicable," he said, adding Britain had "failed to inform or consult Italy, with regard to a military action which could have such consequences."
"A clarification is needed on both the political and diplomatic levels."
Monti talked with his security aides for two hours but didn't issue a statement. He has asked Nigerian President Goodluck Jonathan for details of the failed rescue.
No other casualties were mentioned but witness reports cited in the media said an armored car was involved and there was a lot of gunfire.