Nigeria's military says it has raided a Boko Haram intelligence unit thought to be linked to the recent abduction of more than 200 schoolgirls.
The cell leader Babuji Ya'ari was arrested, a military statement said.
Ya'ari had been actively involved in the seizure of the girls as well as the killing in May of a traditional leader, the emir of Gwoza, the statement added.
More than 2,000 people have been killed this year in attacks blamed on Boko Haram militants.
Ya'ari was a businessman who "participated actively in the abduction of schoolgirls" in the northern town of Chibok, the defence ministry statement said.
He used his participation in a civilian vigilante group fighting Boko Haram to cover up his work spying for the militants, the military said, adding that he had co-ordinated "several deadly attacks in Maidugiri", the capital of Borno state, since 2011.
The military's claims could not be independently verified.
Boko Haram militants abducted more than 200 girls from their school in Borno state on 14 April. Most are still missing.
The group says it will not free the girls until authorities release all imprisoned militants. The government says it knows where the abductees are, but that a rescue could lead to the girls being killed.
The militants have been blamed for several other recent attacks, including an assault on churches near Chibok on Sunday that killed at least 30 people, and a bomb attack on a busy shopping district in Nigeria's capital, Abuja, last week.