A graphic propaganda video clip released by the Islamist militant group Boko Haram shows the execution of dozens of dead male civilians, with a militant leader explaining that the men were killed for being non-believers, and that non-believers in other regions to be invaded by the group should expect the same.

MOSCOW, December 21 (Sputnik) — A graphic propaganda video clip released by the Boko Haram Islamist militant group shows gunmen in a dorm standing over dozens of dead male civilians lying face down, with a gang leader saying that they have been killed because they are non-believers, the Associated Press reports.

The video features a group leader who states: “We have made sure the floor of this hall is turned red with blood, and this is how it is going to be in all future attacks and arrests of infidels.” He added that “from now on, killing, slaughtering, destruction and bombing will be our religious duty anywhere we invade.”

He explained that the dead men were infidel ‘unbelievers’: “You are either Muslim or non-Muslim. You are either a believer or an unbeliever. These people we have killed refused to believe and wanted to remain unbelievers, so we killed them,” he noted.

The video, released to the media on Saturday, is said to have been filmed in November in Bama, northeast Nigeria, Dutch news agency BNO News explained. The release follows reports last week that elements of Boko Haram had been rounding up and killing elderly people in two schools in Gwoza, a town about 60 kilometers to the south of Bama. Bama is said to have been captured by the militants from government forces in early September. BNO News estimates at least 55 victims, possibly more, in the recently released propaganda footage.

Schools are often targeted by the Sunni militant group, whose name is often literally translated as “Western education is forbidden”. The jihadi group, which declared a caliphate in the areas of northeast Nigeria under its control earlier this year, imposes strict Shariah law.

Over 10,000 people have been killed and over 1.5 million driven from their homes over the course of the insurgency, which has also spilled into neighboring countries in Central Africa.