Italy's president has accused Britain of an "inexplicable" failure to consult with his country before a failed attempt to rescue an Italian and a Briton being held in Nigeria by kidnappers who claim ties to al-Qaeda.
The two hostages were killed by their captors before a joint British-Nigerian operation could free them, leading to heavy criticism of the UK, and accusations by Italian politicians that Prime Minister Mario Monti's government is inept in foreign affairs.
Franco Lamolinara, an engineer, and a British hostage, Chris McManus, had been working on a bank construction project when they were kidnapped nine months ago.
"The behaviour of the British government, which did not inform or consult with Italy on the operation that it was planning, really is inexplicable," Giorgio Napolitano, the Italian president, told reporters on Friday.
A top security official in Nigeria said on Friday that authorities had arrested three people in connection with Thursday's operation.
The official did not say whether the suspects were linked to Boko Haram, a radical Islamic group.
The official said that prior arrests had led to information about the hostages, but Al Jazeera's Yvonne Ndege, reporting from Abuja, said the quality of that information was now under scrutiny.
"The failure of the rescue mission is raising questions about the credibility of the intelligence the two countries acted on," she said.
In the town of Sokoto on Friday, blood spatter-coated the walls around the front door of the house where the hostages were kept.
Large-calibre bullet holes had punched through the concrete walls. Locals said they believed the two hostages were killed in a back bedroom.
Residents say the attack lasted about nine hours, with heavy gunfire, and said the military also used an armoured personnel carrier to attempt to storm the compound through an unfinished house behind it.
William Hague, the British foreign minister, was holding talks with his Italian counterpart over the failed rescue attempt at a meeting of European foreign ministers in Copenhagen, while the UK's ambassador was meeting with officials in Rome.
Prime Minister David Cameron's spokesman Steve Field said Monti had not complained over the circumstances of the
operation in a telephone call on Thursday with the British leader.
He also insisted that Monti and the previous Italian government had not raised objections to the possibility of mounting a rescue mission during talks over the last nine months.
Hague confirmed the Italian government was informed about the rescue attempt by Britain on Thursday once the operation was already under way.
"We had to make a decision very quickly to go ahead with this operation, we had very limited time, that constrained how much we were able to consult others,'" Hague said at the meeting in Denmark.
"We were able to inform the Italian government as the operation got under way, but not to do more than that. But I think everybody understands the constraints involved, the rapid timing involved in a case like this."
In a later phone call with Monti, when the hostages had been killed, Cameron had "explained the situation and the reasons for the decision and why we thought it was right for the operation to go ahead", Field said.
British military and intelligence officers had been working within Nigeria for several months ahead of the operation, before a contingent of special forces, drawn from the elite Special Boat Service, were deployed in recent weeks, officials said.
In London, the government's crisis committee of political, military and intelligence officials, known as COBRA, had met about 20 times since the men were kidnapped to consider the case and options to rescue the hostages.
A number of arrests made by Nigerian authorities in recent days had provided more concrete information on the whereabouts of those being held captive, but had also alerted the kidnappers that authorities were on their
British officials said those involved in the operation feared the captors had become aware that the "net was closing" on their location.
"Their very strong advice was that it was important to act, and to act quickly and that offered the best chance of getting those people out," Field said.
"Our opinion, and the opinion of those on the ground was that the hostages were under imminent and grave danger."
He said that the precise details of how and when the two hostages died remained so far unclear, but that the "early indications were that both men were murdered by their captors before they could be rescued".
Al Jazeera's Ndege said the security situation in northern Nigeria was deteriorating.
"The Nigerian authorities have been doing their best to try and get the security situation under control. They have deployed lots of police and military in many of the areas," she said.
She added that much of the deployment in northern states was in places that had experienced attacks by Boko Haram.
"Obviously, news of the kidnap and news of this failed rescue mission will only serve to make people ... a little bit more worried about how in control the security services are," she said.