( CNN ) -- Britain , Italy and Greece on Sunday confirmed that hostages from their countries were among seven construction workers reported killed in Nigeria over the weekend . `` This was an act of cold-blooded murder , which I condemn in the strongest terms , '' British Foreign Secretary William Hague said in a statement announcing that a British construction worker was among the dead . Nigerian militant group Ansar al-Muslimeen claimed responsibility for the February kidnappings of the seven construction workers from an office in northeastern Nigeria . The group , widely known as Ansaru , released images of some of the bodies Saturday . Italy 's Foreign Ministry said Sunday that it appeared the report of the deaths `` is founded . '' Greece said one of its citizens was among the dead , and that his captors `` at no stage either communicated or expressed demands for the release of the hostages . '' Ansaru blamed the deaths on a joint Nigerian-British military operation intended to free the hostages . Without directly addressing the claim , Hague said , `` Responsibility for this tragic outcome rests squarely with the terrorists . '' `` I am grateful to the Nigerian Government for their unstinting help and cooperation , '' he said . `` We are utterly determined to work with them to hold the perpetrators of this heinous act to account , and to combat the terrorism which so blights the lives of people in Northern Nigeria and in the wider region . '' Some of the other hostages were from Lebanon , which had not commented on the reports Sunday . All seven hostages were seized from an office of Lebanese-based construction firm Setraco in northeastern Nigeria on February 18 . In claiming responsibility for the attack , Ansaru said it taken them captive because of `` transgression and atrocities '' against Islam in Afghanistan , Mali and other locations . Setraco 's Nigerian subsidiary is involved in many major road construction projects in northern Nigeria . U.S. officials say Ansaru is an offshoot of the Islamist militant group Boko Haram , which Nigerian authorities say is behind a recent rash of killings and kidnappings in the country . Boko Haram -- whose name means `` Western education is sacrilege '' -- has killed more than 2,800 people in an escalating campaign to impose strict Islamic law on largely Muslim northern Nigeria , according to Human Rights Watch . Ansaru has previously claimed responsibility for the December kidnapping of a French citizen near the border with Niger and for an attack on a prison in Abuja in November . CNN 's Hada Messia in Rome and Per Nyberg in London contributed to this report .
`` This was an act of cold-blooded murder , '' British official says . The hostages had been seized from a construction company office in February . - March 22 :