Lagos, Nigeria (CNN) -- In a meeting Friday with his Italian counterpart, British Foreign Secretary William Hague sought to explain why Rome had not been consulted before a failed rescue attempt that resulted in the deaths Thursday in Nigeria of two hostages -- an Italian and a Briton.
"Mr. Hague made clear that there had been a limited opportunity to secure the release of the two hostages whose lives were in imminent and growing danger," said a joint UK-Italian statement issued by Britain's Foreign & Commonwealth Office. "Under these circumstances it was only possible to inform Italy once the operation was already getting under way."
The meeting between Hague and Italian Foreign Minister Giulio Terzi di Sant'Agata took place at a foreign ministers meeting in Copenhagen.
"Mr. Terzi expressed deep sorrow and disappointment over the tragic outcome of the operation and both ministers agreed on the urgency of sharing full information to facilitate the reconstruction and understanding of these events," the statement said.
Britain's failure to consult Rome before the failed rescue attempt was "inexplicable," the Italian president said earlier Friday.
Italy said Britain did not inform it before the attempt, carried out in conjunction with Nigerian forces, to rescue Briton Chris McManus and Italian national Franco Lamolinara, who were kidnapped last year.
"A clarification on the political-diplomatic level is also needed," Italian President Giorgio Napolitano said.
The kidnappers killed the men while the raid to free them was under way, according to British government sources briefed on the matter.
Nigerian President Goodluck Jonathan has said the men were killed before the joint forces could reach their hideout in the northern state of Sokoto.
A spokesman for British Prime Minister David Cameron told Britain's Press Association the government notified Rome as "the operation was getting under way," describing it as a "very fast-moving" situation.
The UK ambassador to Italy, Christopher Prentice, spoke to Italian authorities in Rome on Friday "on his own initiative to explain events," the British Foreign Office said.
Nigerian forces, with support from Britain, launched the operation after receiving credible information about the captives' location, Cameron said.
McManus and Lamolinara worked for the construction and civil engineering firm B. Stabilini and Co., which is based in Abuja. A message on the company's website Friday read simply "In loving memory of Chris & Franco. RIP from all your friends at B. Stabilini & Co. Ltd."
McManus, 28, was from northwest England, the British Foreign Office said. Lamolinara, 47, and married with two teenage children, hailed from the northern Italian town of Gattinara, the Italian newspaper Corriere della Sera reported.
Jonathan blamed the kidnapping and killings on Boko Haram, the militant Islamist terror group responsible for dozens of attacks in Nigeria in the past two years.
The circumstances behind the men's deaths were unclear, but Jonathan said authorities detained the alleged captors.
"Perpetrators of the murderous act, who have all been arrested, will be made to face the full wrath of the law," the president said in a statement on the government website.
But a statement posted on a pro-jihad forum on which the militant group has been active in recent months denies any link. "The hostage-taking operation was not a Boko Haram one, we have always claimed responsibilities for our attacks, beware allowing the Kaffir [infidel] government of Nigeria to mislead you," it says.
In December, a Nigerian group calling itself "al Qaeda in the land beyond the Sahil" announced that it had captured McManus, according to the Press Association in Britain.
Cameron said he had worked to free the two men since they were kidnapped in May 2011 and authorized the rescue attempt. Authorities could not find the men for months, he said, but eventually got credible information about their location, and "a window of opportunity" presented itself.
"The terrorists holding the two hostages made very clear threats to take their lives, including in a video that was posted on the Internet,'' Cameron said.
"Boko Haram" translates from the local Hausa language as "Western education is forbidden." Authorities have said the militant group is behind attacks that have killed scores of people in recent years.
CNN's Claudia Rebaza, Nkepile Mabuse, Nima Elbagir, and Alex Felton contributed to this report.