In January 2013, Ansaru declared itself a splinter group independent from Boko Haram, the north's main terrorist group, analysts say. Boko Haram, whose name means "Western education is sacrilege," has launched a guerrilla campaign of bombings and shootings across Nigeria's predominantly Muslim north. Boko Haram is blamed for at least 792 killings last year alone, according to an AP count.
Britain previously linked Ansaru to the May 2011 kidnapping of Christopher McManus, who was abducted with Italian Franco Lamolinara from a home in Kebbi state. The men were held for months, before their captors killed them in March 2012 them during a failed Nigerian military raid backed up by British special forces in Sokoto, the main city in Nigeria's northwest.
Boko Haram group earlier claimed the kidnapping in December of a French national working on a renewable energy project in Nigeria's northern Katsina state.
Associated Press writers Sylvia Hui in London and Andrew Meldrum in Johannesburg contributed to this report.
Jon Gambrell can be reached at www.twitter.com/jongambrellAP .