Kano - A vigilante and four female suicide bombers were killed Wednesday at a checkpoint in Nigeria's northeast Borno state after one of them detonated her explosives, according to the National Emergency Management Agency (NEMA).
One bomber blew herself up at a security checkpoint 50 kilometres east of state capital Maiduguri run by civilian vigilantes who help the country's military fight Boko Haram.
Four girls between the ages of nine and 12 were stopped at the checkpoint in Mafa, according to Muhammad Kanar, head of NEMA for the northeast.
"Most of them are abducted from villages and brainwashed before being sent for suicide missions," Kanar told AFP, speaking of the female suicide bombers used by Boko Haram.
"Suicide bombers tried to enter and they were being intercepted for interrogation," Ibrahim Abdulkadir, another spokesman for the agency, told AFP.
"One detonated their bomb," he said, adding "all of them were bombers, all women."
Army spokesman Sani Kukasheka Usman said the three other bombers were shot dead by vigilantes.
Also read: 4 women suicide bombers die near Maiduguri, kill 1
Nigeria's President Muhammadu Buhari has pledged to end the Boko Haram insurgency by the end of the year, but with less than a month to go before his deadline expires the country is still suffering deadly suicide and bomb attacks.
Last month eight people were killed at the same checkpoint when a female suicide bomber blew herself up among women and children arriving in Maiduguri seeking to escape Boko Haram violence in the countryside.
Boko Haram have in recent months been using young women and girls as suicide bombers -- a ruthless new tactic in the six-year-old armed insurgency which has claimed more than 17,000 lives in its bid for a hardline Islamic state in the northeast.
The jihadist group has used the tactic similarly in Cameroon, Chad and Niger.
Many of the girls used as ammunition in Nigeria are unaware they will be blown up, Leila Zerrougui, the UN secretary-general's special representative on children and armed conflict, told reporters in Geneva earlier this week.
Security forces fighting the jihadists said that often the explosive devices are triggered with a remote device, according to the UN expert.