The raid occurred in the northeastern city of Damaturu, previously hit by heavy violence blamed on Islamist group Boko Haram and which last week saw gun battles between security forces and extremists that killed at least 40 people.
However, it was not yet known who the attackers were and whether any Boko Haram members were being held in the jail.
The raid saw attackers throw two explosives and open fire, forcing their way into the central prison in Damaturu, a prison officer said.
State police commissioner Patrick Egbuniwe confirmed the attack on the prison, but said he did not yet have further details.
“A prison guard responded and there was a shootout, but the attackers overpowered the prison guards and broke into the prison,” said the officer, who was not there at the time but gathered information from colleagues.
“Four guards were killed and an unspecified number of the attackers were shot, but their comrades took them away.”
Boko Haram’s insurgency has killed hundreds, mainly in Nigeria’s north. The group has previously targeted prisons and freed Boko Haram members.
On Friday, President Goodluck Jonathan fired his national security adviser and defence minister amid growing fears over spiralling violence in the north of Africa’s most populous nation and largest oil producer. — AFP.



