Kano - Gunmen have raided a prison in Gwoza, a border town with Cameroon, freeing 170 inmates and killing a civilian, officials and residents said on Friday.
The civilian was shot dead in crossfire when the gunmen in cars and on motorcycles stormed the prison on Thursday in Gwoza, 130km from Maiduguri, the hotbed of Boko Haram Islamists, they said.
"There was a total of 170 inmates in the prison and all of them were freed by the gunmen who overwhelmed us with their superior fire power," a prison warden involved in the shootout, who requested anonymity, told AFP.
"They set fire to the administrative building but spared the inmates' rooms which they broke into and set all of them free," he said.
"A civilian was killed by a stray bullet during the shootout," he added.
Resident Zakari Kyari said the gunmen had taken part in the evening prayer at a nearby mosque before storming the prison.
"Around 19:00 just after the prayers the gunmen opened fire on the prison, chanting 'Allahu Akbar' and the wardens returned gunfire which led to a shootout," he said.
Two other residents gave a similar account of the prison raid.
The spokesperson for the joint military task force in the area, Sagir Musa, said he was not aware of the attack.
It was not clear if the attackers were members of Boko Haram who have been blamed for scores of attacks in the area, or criminal gangs that also operate in the region.
On 5 March, gunmen killed nine people, including two policemen in an overnight raid on a police station in Gwoza.
Nigeria has seen an upsurge in the Boko Haram insurgency in recent years. Violence blamed on the extremists has claimed some 3 000 lives in northern and central Nigeria.