The massive jailbreak occurred before dawn on Monday in Owerri, the capital of Imo state. Attackers wielding machine guns, rocket-propelled grenades and explosives stormed the facility, blasting their way through the administrative block to gain entrance to the prison yard. They exchanged fire with on-duty guards "in a fierce gun battle" and "forcefully released a total of 1,844 inmates in custody," according to a press release from the Nigerian Correctional Service, the government agency in charge of the West African nation's prison system.
While most of the inmates fled, 35 stayed behind and at least six others have voluntarily returned to the prison. Authorities are investigating the incident and have launched a manhunt to recapture the escaped detainees, the Nigerian Correctional Service said.
The gunmen also attacked other government buildings in Owerri, including the Imo state headquarters of the Nigeria Police Force, the country's leading law enforcement agency. There were no deaths or injuries among police, apart from a constable who sustained a minor bullet wound to his shoulder.
"The attempt by the attackers to gain access to the police armory at the headquarters was totally and appropriately resisted," the Nigeria Police Force said in a statement Monday, adding that its inspector-general has ordered the "immediate deployment" of additional police units in Imo state.
There was no immediate claim of responsibility, but the Nigeria Police Force blamed the Eastern Security Network (ESN), the paramilitary wing of a secessionist movement active in the region known as the Indigenous People of Biafra (IPOB). The group seeks to restore independence to the so-called state of Biafra in southeast Nigeria. Biafra secessionists had declared independence in 1967 but were defeated by the Nigerian federal government in a nearly three-year civil war that left 1 million people dead.
“IPOB and ESN were not involved in the attack in Owerri, Imo state," the spokesman said. "It is not our mandate to attack security personnel or prison facilities."
ABC News' James Bwala contributed to this report.