The Foreign Office was last night investigating claims that a British citizen is among seven foreign hostages, including three Lebanese citizens, and one each from Greece, Italy and the Philippines, murdered by a terrorist group in Nigeria.
The report of the killings comes almost exactly a year after a failed rescue bid by British and Nigerian forces resulted in two hostages, one a Briton, being killed by their captors.
The Ministry of Defence refused to comment on claims by the Islamist group Ansaru – linked to the extremist organisation Boko Haram – that the murders were provoked by the arrival of British fighter jets in Nigeria amid rumours of a rescue mission.
Photographs of the dead hostages, who were kidnapped from Setraco, a Lebanese construction company in the northern state of Bauchi last month, are understood to have been posted on an Islamist website by the group.
In a statement, it claimed that sightings of British military planes in the region, and a message from the President of Nigeria, Goodluck Jonathan, that the government would do anything in its power to free the hostages, had triggered the decision.
"[We] announced the capture of seven Christian foreigners and warned that ... any attempt by force to rescue them will render their lives in danger," the statement said.
"The Nigerian and British government operation led to the death of all the seven Christian foreigners," it added.
Ansaru's full name is Jama'atu Ansarul Muslimina Fi Biladis Sudan, which roughly translates as "vanguards for the protection of Muslims in black Africa".
The Foreign Office stated yesterday: "We are aware of reports of the death of a British national in Nigeria and are urgently investigating". It asked "the media not to speculate at this extremely sensitive time".
Last night, Nigerian officials cast doubt on the claims by Ansaru. "As far as I'm concerned, and to the best of my knowledge, nothing like that has happened," said the Bauchi police commissioner, Mohammed Ladan.
According to news agencies, an intelligence official in the north also said he doubted the report, although he said some suspects linked to the kidnapping had been arrested last week. And Mohammed Abdullah, a spokesman for Setraco, also stated that he had heard nothing of any harm done to the hostages.
In what appeared to be a carefully planned attack, the workers had been taken during a raid on the company's compound in Jama'are, about 200 kilometres north of Bauchi, on 16 February. Gunmen first attacked a local prison, destroying police trucks, before they assaulted the compound during which a guard was killed.
The reported deaths of the hostages come a year after a bungled British-Nigerian rescue mission in Sokoto, in the north-west of Nigeria, saw two hostages, a Briton, Chris McManus, and an Italian, Franco Lamolinara, killed before special forces soldiers could get to them. Ansaru was linked to the kidnapping, which took place in May 2011.
Ansaru declared itself a splinter group independent from Boko Haram, Nigeria's main terrorist group, earlier this year, according to analysts. Boko Haram has so far been blamed for almost 800 killings last year alone.