In a statement emailed to journalists, Ansaru “announces to the world, especially the French government, that it was responsible for the abduction of engineer Francis Collomp…63, working for the French company Vergnet.”
A security guard and one of Collomp’s neighbours were killed in the abduction.
Ansaru says the kidnapping was in response to France’s role in pushing for an intervention force to drive out Islamists who have taken over northern Mali.
It also blamed “the stance of the French government and the French people on Islam and Muslims,” in particular a law banning the niqab.
"We inform the French government that this group will continue launching attacks on the French government and French citizens...as long as it does not change its stance on these two issues," the statement continued.
Little is known about Ansaru, which is believed to be an off-shoot of Boko Haram, a militant group in northern Nigeria responsible for a series of deadly attacks.
Ansaru is listed by the UK government as a terrorist organisation with links to Al-Qaeda in the Islamic Maghreb [AQIM].
On Friday, French President said a group with links to AQIM probably kidnapped Collomp, but did not specify which one.