Armed men have broken into a jail in Nigeria using bombs and heavy gunfire, freeing 119 inmates¹, officials say.

尼日利亚官员称，武装分子利用炸弹和重武器攻入一座监狱，释放了119名囚犯。

A prison service spokeswoman told the BBC the armed men killed a jail officer during the attack, in the central Kogi state, on Wednesday evening.

Most of the prisoners were awaiting trial and none were high-profile detainees, according to officials.

Islamist militant² group Boko Haram later said it carried out the attack, freeing seven of its members.

The group has carried out similar jailbreaks before, including a massive 2010 attack on a prison further north in Bauchi state.

In that incident Boko Haram freed about 700 prisoners, many of whom were members of the group.

'No lifers'

A police officer, who requested anonymity³（匿名） , told Nigeria's Daily Trust newspaper that about 20 gunmen on motorbikes stormed the jail in Koton-Karifi, about 160km (100 miles) south of the capital Abuja.

He said the attack, launched at about 19:00 local time (18:00 GMT) on Wednesday, lasted for about 30 minutes.

An eyewitness⁴ told the paper: "After bombing the gate, they immediately moved into the prison shooting sporadically⁵（零星地） in order to chase other prison officers away."

Hadijha Aminu, from the Nigerian Prisons Service, told the BBC that the attackers had freed all but one of the inmates from the federal prison.

"There were no high-profile prisoners - no lifers," she said.

A warden⁶ was killed when attackers forced open the gates of the jail and then freed 119 inmates.

Police later said they had recaptured 25 of the detainees.

On Thursday evening, Boko Haram said it had staged the attack. A spokesman for the group said they had freed seven of their members and taken them to camps.

The authorities appear to be struggling to contain Boko Haram's attacks on state institutions, despite the recent arrest of a senior member of the group and a crackdown against members in a northern stronghold, the BBC's Mark Lobel in Lagos reports.

Last month, Boko Haram freed some of its captured members during a series of bombings on police stations in the northern city Kano.

Boko Haram, whose name means "Western education is forbidden", wants to establish Islamic law in Nigeria.