DAKAR, Senegal — An affiliate of the Islamic State in Nigeria has claimed responsibility for the execution of 11 people, saying the killings were in retaliation for the death of the ISIS leader Abu Bakr al-Baghdadi in Syria in October.

A video released on Thursday showed members of the Nigerian affiliate slashing the throats of 10 people and shooting an additional person. A voice-over says the killings are a “message for Christians” and that all of those killed were Christian, although Nigerian experts said some of them were probably Muslims, based on previous episodes involving the group.

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