At least 15 Christians were killed by suspected Boko Haram militants in northern Nigeria on Dec. 28 when the militants snuck into Musari, a neighborhood on the outskirts of Maiduguri, early in the morning and slit the throats of the Christians in their own homes, International Christian Concern reports. Nigerian military officials -- who often under-report the casualties in Boko Haram attacks -- put the death toll at five, but residents of Musari and other relief organizations put the number at 15. According to a resident, the militants were specifically targeting Christians because they broke into only Christian homes in an area of Musari that is predominantly Christian. A relief official added that the victims "were selected because they were all Christians, some of whom had moved into the neighborhood from other parts of [Maiduguri] hit by Boko Haram attacks." Since beginning its armed insurgency in 2009 in a campaign to establish an Islamic state in Nigeria's north, Boko Haram has killed more than 3,000 people in Nigeria. Christians in the region continue to live in a constant state of fear amid an increasing number of bombings, shootings and violent attacks.