Unknown gunmen on Saturday attacked Minna Medium Prison, broke into the cells and set 270 inmates free.
Three of the gunmen, dressed in long caftans, stormed the facility at about 4.30p.m.
It was gathered that as soon as the three entered the prison, they started to fire gun shots into the air and ordered all the inmates out.
They overpowered and disarmed the prison officials, broke into the records and armoury rooms and carted away some weapons and bullet proof vests.
It was also gathered that scores of other gunmen took strategic positions around the prison in an operation that lasted 10 minutes.
A security man, who was injured at the entrance of the prison, is receiving treatment in an undisclosed hospital in Minna.
A prison official, who requested not to be named, said two notorious armed robbers were among 270 inmates who escaped with the gunmen.
“We had 323 inmates in our various cells but we are left with only 53 in one of the cells,” he said. “Our gateman was injured; they broke into our armoury and carted away weapons and bullet proof vest.
“From where I took cover, I saw Osama, one of the notorious armed robbers in the prison firing shots into the air. I want to believe his gang brought the gun and I saw him leading Ayo (Eze Ego), a dismissed Mopol and other inmates, out.”
The armed men later snatched a Honda Car and escaped with it.
The spokesperson, Nigeria Prison Service, Niger state command, Rabiu Mohammed, confirmed the incident, but said it was an attempted jail break.
The state Commissioner of Police, Emmanuel Amore, who visited the scene, said his men found four of the inmates that escaped and that he has directed a massive manhunt for the other inmates.
He also said a Sienna Toyota car with four AK47 rifles, believed to have been used by the gang, were impounded.
He said investigation had commenced.