Nigerian government sources had said British construction worker Chris McManus, 28, and Italian engineer Franco Lamolinara, 47, were killed by Boko Haram members in Sokoto in retaliation for a botched rescue attempt led by British forces.
But The Guardian, Oshodi, Nigeria, reported Boko Haram spokesman Abul Qaqa told reporters in a telephone interview Friday: "We have always claimed responsibilities for the operations we undertake, but we are not responsible for the killing of the said foreigners in Sokoto on Thursday."
McManus and Lamolinara, who had been working on a construction project for an Italian building company, were kidnapped in Birnin Kebbi May 12.
Some Italian lawmakers had complained the Italian government had not been told of the rescue operation in advance.
Steve Field, British Prime Minister David Cameron's spokesman, said Italian Prime Minister Mario Monti had not complained about the circumstances of the rescue during a phone call Thursday with Cameron, the Nigerian Tribune reported.
British Foreign Secretary William Hague said British officials had told the Italian government about the rescue attempt once it began Thursday.
He said British officials feared the hostages' captors had become aware the "net was closing" in on them.
"We had to make a decision very quickly to go ahead with this operation; we had very limited time," Hague said. "That constrained how much we were able to consult others."