What you need to know:
- In a separate incident, a military base in northwest Zamfara state was attacked at the weekend.
Heavily armed gunmen stormed a jail in Nigeria's central Kogi state overnight, freeing scores of inmates, a prison spokesman said Monday.
It was unclear who the gunmen were but central and northwest Nigeria have been terrorised by criminal gangs for years.
"The medium Security Custodial Centre in Kabba, Kogi State, has been attacked by yet to be identified gunmen and 240 inmates forcefully released," Nigeria's correctional service spokesman Francis Enobore said in a statement.
At about 2245 GMT on Sunday, he said, numerous attackers "engaged the armed guards in a fierce gun battle."
The gunmen invaded the prison, which had 294 prisoners in custody at the time, including 224 pre-trial detainees.
Investigations were under way Monday to find the escapees, he added.
In a separate incident, a military base in northwest Zamfara state was attacked at the weekend.
Gunmen killed 12 Nigerian security forces in that attack, two security sources said Monday.
Large prison outbreaks are not uncommon in Nigeria.
In a recent brazen attack on April 5, gunmen raided Owerri police headquarters, freeing more than 1,800 inmates.
Jihadist group Boko Haram, who launched an insurgency in northeast Nigeria in 2009, have frequently attacked prisons to free inmates.
In February 2012, dozens of gunmen bombed their way into a prison in Kogi state's Koton Karfe, freeing 119 and killing a warden.
The attack was claimed by Boko Haram who said they freed members being detained in the prison.
In November 2014, gunmen blasted into the same prison with explosives and freed 132 of the 145 inmates in the facility.
Again in 2018, at least 14 people escaped from the same prison.
Nigeria's security forces are often described as overstretched and overwhelmed.
In addition to fighting jihadists in the northeast and criminal gangs in central and northwestern Nigeria, the armed forces are also facing separatist agitation in the southeast.
At least 127 police and security personnel have been killed this year in the region and dozens of police stations razed.
A paramilitary group known as the Eastern Security Network or ESN has been blamed for the attacks, but have denied any responsibility.