The Islamist group, Ansaru, that killed seven foreign hostages it had been holding since February has posted a video of what it said was their bodies on the Internet.
Italian and Greek authorities confirmed on Sunday that a Briton, an Italian, a Greek and four Lebanese construction workers abducted in Bauchi State last month had been killed by their captors.
British Foreign Secretary William Hague said it was “likely” the hostages were dead, calling it “an act of cold blooded murder”.
The police declined to comment and Interior Minister Aba Moro told the BBC Hausa service on Monday there was no confirmation the hostages were dead.
“As long as it remains unconfirmed, efforts will be made to ensure their rescue and security”, he said.
The silent video published by the al Qaeda-linked group Ansaru and dated March 9 shows a gunman standing next to a pile of bodies, then close-ups of their faces lit up by a torch.
It carries the Arabic title “The killing of the seven Christian hostages in Nigeria” although the religion of the captives was not clear.