More than 1,800 prisoners have escaped from Nigerian prison after being attacked by militants armed with grenades, machine guns, explosives, and rifles, BBC reported.

The attackers used explosives to detonate the administrative building of the prison in the southeastern town of Owerri and enter the prison courtyard. Owerri is located about 400 km southeast of Nigeria's largest city, Lagos.

The Nigerian correctional service confirmed to the BBC that 1,844 prisoners escaped after the attack on Monday.

Nigerian police have accused the banned separatist organization of the attack on the prison. AFP reported that the group has denied any involvement.

Since January, there have been some attacks on police stations in southeastern Nigeria, and large quantities of ammunition have been stolen since January, according to the BBC. None of the groups claimed responsibility for these attacks.