ABUJA: More than 1,800 inmates have escaped after heavily armed men attacked a prison in southern Nigeria using explosives, prison authorities said Monday, in one of the country’s largest jailbreaks.

The attackers blasted their way into the Owerri prison in Imo state, engaging guards in a gun battle, 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.

President Muhammadu Buhari in a statement called the attack an “act of terrorism” 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 after the prison escape, a statement said, to protect local residents. Imo state is part of a region that has long been a hotbed for separatist groups and where tensions between federal authorities and the indigenous Igbo population are often high.