Many prisoners are feared dead in the failed jailbreak bid at the Abakaliki Prisons in Ebonyi State on Thursday.
The attempt was made at about 9:30am on Thursday.
The jailbreak attempt was said to have been brought about by some inmates of the prison who refused their cells being searched as it is customary every morning.
However, some other sources said the inmates were protesting poor conditions in the prison.
The prison, which was built during the colonial era, was said to be meant for about 200 inmates but now has over 1,000.
The Ebonyi State Governor, Dave Umahi, confirmed the congestion in the prison.
No fewer than 15 inmates were feared dead after the authorities of the prison invited armed policemen and soldiers to join its own security in quelling the riot.
Some prison officials were said to have been injured also.
The State Comptroller of the Nigerian Prisons Service, Emilia Oputa, however denied that anyone died in the riot.