"The bomber was a girl aged around 15 who was seen around the mosque when worshippers were preparing for the afternoon prayers," vigilante Danlami Ajaokuta said of Thursday's attack in Malari village, adding 12 had died and seven were injured.
"People asked her to leave because she had no business there and they were not comfortable with her in view of the spate of suicide attacks by female Boko Haram members.
"She made to leave but while the people were inside the mosque for the prayers she ran from a distance into the mosque and blew herself up," he added -- an account corroborated by resident Gajimi Mala. There was no immediate claim of responsibility but Boko Haram has used both men and young women and girls as human bombs in the past, and Borno state where the attack took place has been the hardest hit by the insurgency.
The attack comes just a day after Boko Haram militants gunned down at least 145 people in three Borno villages, shooting Muslim worshippers during the holy month of Ramadan in the bloodiest day of attacks since new President Muhammadu Buhari came to power.