The Islamic State released a video on Tuesday showing the execution of eleven hostages, reportedly in retaliation for the deaths of ISIS leaders Abu Bakr al-Baghdadi and Abu al-Hassan al-Muhajir.
Baghdadi, the supreme leader or “caliph” of the Islamic State, was killed in Syria by U.S. special forces on October 26. The next day, U.S. airstrikes killed ISIS spokesman Abu al-Hassan al-Muhajir.
The hostages included ten Christians and one Muslim. Two more Muslim hostages were spared from execution. The full group of 13 hostages appeared in a video released on December 17 in which they asked the Christian Association of Nigeria to negotiate with the Islamic State to secure their release.
“The Secretary-General recalls that attacks by a party to an armed conflict that target civilians, aid workers, and civilian infrastructure violate international humanitarian law,” read a statement from the U.N. Secretary-General. “Those responsible for these atrocities must be held accountable.”