LAGOS, Nigeria (AP) — Nigeria's government on Friday condemned extremists linked to the Islamic State group after a video circulated of 11 hostages, most of them Christians, being executed. They were thought to be killed on Christmas Day.

President Muhammadu Buhari said in a statement he was “profoundly saddened and shocked by the death of innocent hostages in the hands of remorseless, godless, callous gangs of mass murderers that have given Islam a bad name through their atrocities.”

The extremist group, which calls itself the Islamic State West Africa Province, said the captives were executed as revenge for the killing of Islamic State group leaders in Iraq and Syria in October. The video was circulated Thursday.

Buhari urged Nigerians not to allow the killings to divide them along religious lines, saying “these agents of darkness are enemies of our common humanity."

The extremists who abducted the victims in November are believed to be part of a group that split from the Boko Haram insurgency in northeastern Nigeria and pledged allegiance to the Islamic State group.