Its release came days after the terrorists announced the kidnapping of 14 people including two aid workers and, according to them, six members of the security forces.
It shows three men in plain clothes kneeling in a field, introducing themselves as members of the Nigerian security forces before masked men in fatigues open fire on them shouting “Allahu Akbar” (God is greatest).
“We tell the Nigerian army that we will never spare those fighting against the people who follow Allah’s religion,” one of the executioners said in Hausa, a language widely spoken in the north of the country.
“We will attack your bases and confront you on your routes,” the terrorists added, shortly before the execution.
Those abducted last Wednesday included two Red Cross workers.
ISWAP claimed responsibility for the kidnapping, saying six members of the Nigerian security forces were among the hostages.
ISWAP focuses on military targets, while Boko Haram mainly attacks civilians.