More than 180 inmates in a medium-security prison in central Nigeria were at large after unidentified gunmen opened fire on the facility, the government said on Monday.

The attack happened late Sunday at the jail in the Tunga area of the Niger state capital, Minna. Guards were overpowered and inmates were able to escape.

"There was a jailbreak at Minna Medium Security Prison, located at Tunga area of Minna Metropolis, perpetuated by armed criminals who attacked the prison and gain access after an exchange of fire with prison armed men," Jibrin Baba Ndace, a spokesman for the Interior Ministry, said in a statement.

Ndace quoted Interior Minister Abdulrahman Dambazau as blaming the incident on "security gaps in the prisons such as manpower and decongestion".

"Out of the 210 inmates that escaped from prison custody, 28 have been re-arrested while 182 are still at large," Dambazau previously told reporters.

An investigation has begun but it was not immediately clear who or what was behind the incident.

Nigeria's prisons are known to be congested, among other problems, as a result of the notoriously slow justice system which sees thousands of suspects (awaiting trial) being remanded in prisons for years.

Dambazau said the government is building a 3,000-inmate capacity prison in each of Nigeria's six geopolitical zones and recruiting 6,000 personnel to address some of the problems.

In November 2014 a group of gunmen armed with explosives blasted a prison in the town of Koton Karfe, in Kogi state, which neighbors Niger to the south: 132 inmates escaped.

In 2012 the same prison was raided by gunmen who freed more than 100 inmates. Boko Haram terrorists claimed responsibility and said its fighters were being kept in the facility.