The so-called Islamic State West Africa Province (ISWAP), which is an offshoot of IS, executed the group of captives, the majority of whom were Christians. A video showing a group pleading for help was released by the terrorists earlier this month. Local media reported there were 10 Christians and three Muslims shown in the footage, meaning at least one Muslim is among the dead.
ISWAP said it spared the lives of two of its captives.
A member of the group’s media unit said the massacre was in revenge for the killings of al-Baghdadi, who was wiped out in a US mission in northwestern Syria in October.
They said: “We killed them as a revenge for the killings of our leaders, including Abu Bakr al-Baghdadi and Abul-Hasan al-Muhajir in Iraq and Syria.”
Nigerian media analysed the footage of the killings and compared it to the earlier video.
The clip released on December 17 appears to show 12 men and one woman sitting on the ground.
United Nation Secretary General Antonio Guterres responded to the Christmas massacre by offering his condolences to the families of the victims.
His spokesman Stephane Dujarric said: “The Secretary General is deeply concerned about reports that civilians have been executed and others abducted by an armed group in northern Borno State, northeastern Nigeria.
READ MORE: NIGERIA CIVIL WAR: Clashes between Christians and Muslims could SPIRAL
The kidnappings sparked international outrage and the group’s leader claimed all girls had converted to Islam and been “married off”.
The killing of al-Baghdadi dealt a huge blow to the so-called Islamic State in Syria and Iraq.
While President Trump has claimed ISIS is defeated analysts have warned its ideology is not dead.
In his first Christmas message as Prime Minister, Boris Johnson vowed to defend persecuted Christians around the globe.
He said: “Today of all days, I want us to remember those Christians around the world who are facing persecution.
“For them, Christmas Day will be marked in private, in secret, perhaps even in a prison cell.
“As Prime Minister, that’s something I want to change. We stand with Christians everywhere, in solidarity, and will defend your right to practice your faith.”