Boko Haram offshoot claims responsibility in Nigeria kidnapping February 18, 2013 -- Updated 1317 GMT (2117 HKT) NEW: Militant group Ansaru claims responsibility for kidnapping of 7 foreign workers NEW: Ansaru is believed to be an offshoot of Boko Haram, U.S. officials say (CNN) -- A Nigerian militant group previously linked to the kidnapping of a French citizen claimed responsibility Monday for taking seven workers from a construction company's offices in northeastern Nigeria. In an e-mail sent to reporters, Ansaru said it had kidnapped the seven workers Saturday because of "transgression and atrocities" against Islam in Afghanistan, Mali and other locations. Those kidnapped included workers from Italy, Greece and Lebanon, those governments confirmed. Gunmen took the workers from the offices of Setraco, a construction company in Jama'are, in Bauchi State, police said. In December, the group claimed responsibility for the kidnapping of a French citizen near the border with Niger and for an attack on a prison in Abuja in November. 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. Incidents have included the killings of three North Korean doctors in northern Yobe and the killings of nine people working for a government polio vaccination program in the northern city of Kano this month. Nigeria launched a military crackdown on Boko Haram in January. Security forces have since captured one of the group's leaders and killed 17 suspected Boko Haram members. In the past, the group attacked other Muslims who it said were on an immoral path. But the U.S. State Department has accused the group's leaders of having ties to the al Qaeda terrorist network and of hoping to drive a wedge between Nigeria's Christian and Muslim communities. CNN's Vladimir Duthiers and journalist Hassan John contributed to this report.