At least 1,800 inmates escape after gunmen storm Nigerian jail

More than 1,800 inmates have escaped after a heavily armed gang attacked a prison in south-eastern Nigeria using explosives, correctional authorities said Monday -- in one of the West African country's largest jailbreaks.

The attackers blasted their way into the Owerri prison in Imo state, engaging guards in a gun battle and breaking out inmates, the national corrections authority said in a statement.

"I can confirm that the Imo State Command of the Nigerian Correctional Service was attacked by unknown gunmen in Owerri," Imo state corrections service spokesman James Madugba told AFP, adding that the number of escaped inmates was yet to be confirmed.

"The situation is under control," he said.

The assailants arrived in pickup trucks and buses before storming the facility, the correction authority said.

No group claimed responsibility for the assault, though President Muhammadu Buhari called the attack an "act of terrorism" carried out by "anarchists" and urged security forces to capture the assailants and the escaped detainees.

The governor of neighbouring Abia state imposed a night curfew on two towns there, a statement said, to protect local residents without direct reference to the prison attack.

Prisons in Africa's most populous country are often overcrowded, and as many as 70% of inmates are on remand and can be held awaiting trial for years.

Buhari is facing several security challenges including a more than decade-long jihadist insurgency in Nigeria's northeast, a spate of mass kidnappings by criminal gangs in the northwest and a surge in piracy on commercial shipping in the Gulf of Guinea off the coast.