Nigerian troops have arrested a businessman accused of "participating actively" in Boko Haram's mass abduction of nearly 300 schoolgirls from a town.

Defence Ministry spokesman Major General Chris Olukolade said Babuji Ya'ari headed a "terrorists' intelligence cell" for the Islamic extremists while masquerading as a member of the self-defence Youth Vigilante Group.

That confirms suspicions the vigilantes have been infiltrated by Boko Haram. Soldiers have said some of their comrades also belong to Nigeria's home-grown Islamic extremist group.

"The arrest of the businessman has also yielded some vital information and facilitated the arrest of other members of the terrorists' intelligence cell who are women," Maj Gen Olukolade said.

He said that since 2011, Mr Ya'ari had co-ordinated several deadly attacks on the north-eastern city of Maiduguri, the birthplace of Boko Haram, and spearheaded the May 2014 assassination of the emir of Gwoza, a religious and traditional ruler who was targeted for speaking out against Boko Haram's extremism.

Boko Haram was responsible for the April 2014 kidnapping of 273 girls from a boarding school in Chibok, in Nigeria's north east. Dozens escaped but 219 schoolgirls remain missing.

The mass abduction sparked international outrage and demands for the girls' release under the Twitter hashtag BringBackOurGirls.