9 March 2012 Last updated at 11:51 GMT
Italian president Giorgio Napolitano has said it is “inexplicable” that the UK did not informed his government about a bid to rescue a Briton and an Italian held hostage in Nigeria.
Chris McManus, 28, from Oldham, Greater Manchester, and Franco Lamolinara died in the attempt by UK Special Forces and Nigerian military on Thursday.
The UK prime minister said the men’s lives had been in “imminent danger”.
The engineers, abducted last May, were held by an Islamist group in Sokoto.
Mr Napolitano was quoted in the Italian media as saying: “The behaviour of the British government, which did not inform or consult with Italy on the operation that it was planning, really is inexplicable.”
He called for a political and diplomatic explanation from the UK.
The house where the men were being held had been under surveillance for some time.
BBC reporter Haruna Shehu Tangaza in Sokoto described several hours of heavy fighting and said he also saw the bodies of two Nigerians.
Reports have emerged that a senior member of militant Islamist group Boko Haram was captured on Tuesday, and he gave information which led forces to the house where the two construction engineers were being held.
It has been reported that the kidnappers turned their guns on the men even before the joint British and Nigerian military operation, involving the UK’s Special Boat Service, entered the compound.
Both the UK prime minister and Nigerian President Goodluck Jonathan said they believed the kidnappers had killed them.
In a statement after the operation, Mr Cameron said: “The early indications are clear that both men were murdered by their captors”.
But an unnamed official from the Nigerian state security service quoted in local reports said the hostages died in the crossfire.
BBC security correspondent Gordon Corera said events on Thursday were fast-moving.
British officials spoke of a collapsing timeframe, with fears that the chance of a rescue might close as the men were either moved or killed.
‘Window of opportunity’
News of the operation broke in a statement from the office of Italian Prime Minister Mario Monti.
It used very similar language to that used by the British side but made it clear the Italians were told the military option was being used only after the operation had started.
Mr Monti chaired a meeting of a government security committee to discuss the failure of the attempt to rescue the hostages. The meeting ended after two hours without any comment being issued.
Italian Senator Lucio Malan told BBC Two’s Newsnight programme that the Italians were not satisfied and wanted to know why they had not been consulted.
“It is quite uncommon that a country that is involved is not informed before. Apparently it was a very difficult situation and it might have been the best decision but it is still to be explained why the Italian authorities haven’t been informed,” he said.
Mr Cameron said the decision to act had been taken at very short notice.
He said: “A window of opportunity arose to try and secure their release. We also had reason to believe that their lives were under imminent and growing danger.”
Downing Street said the UK had been in regular contact with the Italian authorities throughout the operation.
A spokesman said Rome had been informed when the rescue bid was under way and the British prime minister spoke to his Italian counterpart when it had finished.
Commons Foreign Affairs Select Committee chairman Richard Ottaway said the UK was not duty bound to tell Italy about the operation in the circumstances.
He told the BBC: “I can understand the concerns and frustrations of Italian politicians but I think they’ve got to accept and recognise that these are very fast-moving, delicate operations and it’s not always possible to keep politicians briefed in advance of what goes on.
“I’m not convinced that having briefed them in advance would have enhanced the safety of the Italian hostage in any event.”
Mr Monti’s office said he had asked Mr Jonathan to provide a “detailed reconstruction” of events as soon as possible.
The Nigerian president described it as a “deeply sad and regrettable incident”.
Mr Jonathan said that the men’s captors had been seized and “would be made to face the full wrath of the law”.
He said they were from Boko Haram, which has carried out a number of attacks on police, politicians and clerics who oppose the group.
Our security correspondent said Boko Haram has become more violent and capable in recent years and there is a suspicion this may be a sign of the growing influence of the group al-Qaeda in the Islamic Maghreb.
Italian senator Lucio Malan: ‘Usually in these cases the other countries are informed before the operation is started’
Al-Qaeda in the Islamic Maghreb has a track record of kidnapping Westerners in north Africa and trying to extract ransom payments to fund its violence.
Gunmen seized the two men in the town of Birnin Kebbi in the north of Nigeria on 12 May 2011.
They worked for Italian firm B Stabilini in the construction of a local headquarters for the Central Bank of Nigeria.
Relatives of Mr McManus released a statement saying they were “devastated” by his death but thanked those who had worked to try to free him.
“During this ordeal we have relied heavily on the support of our family and friends which has never waned and has enabled us to get through the most difficult of times,” they said.
Elizabeth Donnelly, head of the Africa Programme at international affairs think tank Chatham House, said there was very little information about the group that captured the men.
She said: “What is interesting about this is, from what I understand, the demands of the group that were holding the hostages had been changing.
“This suggests that there may have even been conflicts within the group, whichever group it was.”
The Foreign Office advises against all travel to some areas of Nigeria and against all but essential travel to other areas, but these do not include the area where the men were kidnapped.
It says there is the threat of kidnap and terrorism across the west African country.