A jihadist group, the Islamic State West Africa Province, has killed five aid workers abducted last month in Borno State.
A France-based group, Action Against Hunger, announced the development on Wednesday.
The announcement came after the insurgents released a video online which showed the execution of the five men.
“It is with profound grief that we confirm the murder of Ishaku Yakubu, Action Against Hunger (ACF) staff member from Monguno, and four other aid workers,”Action Against Hunger said in a statement.
The statement said the humanitarian workers were taken hostage by the armed group in Borno State, North-East Nigeria, on June 8.
“This unjustifiable killing reflects the immense difficulty faced by independent and impartial humanitarian actors, and the violence we are exposed to every day to fulfil our mission,” the statement added.
Aid group International Rescue Committee (IRC) confirmed that one of its employees, Luka Filibus, was also among those killed.
“The IRC strongly condemns the senseless execution of our colleague, Luka Filibus, and his fellow humanitarian captives.
“We condemn this barbaric treatment and demand the immediate return of his remains to his family,” IRC said.
Humanitarian workers have been repeatedly targeted by jihadist groups waging a decade-long insurgency in North-East Nigeria.
President Muhammadu Buhari expressed sympathy for the families of the five aid workers and pledged the jihadists would be “wiped out completely”.
“Security agencies in the state will work closely with their organisations to implement measures to ensure that no such kidnapping of staff occurs again,” a statement from the presidency said.
The 10-year conflict in North-East Nigeria has killed 36,000 people and displaced about two million from their homes.
Last year fighters from the Islamic State West Africa Province (ISWAP) faction abducted a group of six humanitarian workers — including a female Acton Against Hunger employee — in the region.
Five of the hostages were later executed and the ACF worker remains in captivity.
ISWAP broke away from jihadist group Boko Haram in 2016 and swore allegiance to then Islamic State leader Abu Bakr al-Baghdadi.