An ISIS related organisation 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.

The members of the Islamic State West Africa Province, which is known by the acronym ISWAP, left the Islamic militant group Boko Haram in 2016. According to the International Crisis Group, it has between 3,500 and 5,000 fighters. Its leaders split from Boko Haram in part because they disapproved of the violence that the group and its harsh leader, Abubakar Shekau, has meted out to fellow Muslims.

The video was released to Ahmad Salkida, a Nigerian journalist who often publishes information about both ISWAP and Boko Haram. According to Mr. Salkida, ISWAP had shown interest in negotiating a prisoner swap, but abruptly changed course and executed the prisoners instead.

The 56-second video shows the captives, who were blindfolded and wearing orange tunics, kneeling on the ground, their captors standing behind them in black balaclavas.

During the video a voice-over says: “This message is to the Christians in the world. Those who you see in front of us are Christians, and we will shed their blood as revenge for the two dignified sheikhs, the caliph of the Muslims, and the spokesman for the Islamic State, Sheikh Abu al-Hassan al-Muhajir, may Allah accept them.”

The earlier video showed the all-male captives appealing for the Christian Association of Nigeria and President Muhammadu Buhari to intervene and save them.

The footage was possibly an attempt to divide the country’s Muslim and Christian populations and pile pressure on the government to respond to militants’ demands, security analyst Kabiru Adamu told the BBC.

President Buhari said of the killings:

We are 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.

We should, under no circumstance, let the terrorists divide us by turning Christians against Muslims because these barbaric killers don’t represent Islam and millions of other law-abiding Muslims around the world.