Nigeria's military has freed a number of women and children held hostage by Islamist sect Boko Haram, the army said on Saturday, after its offensive in the northeast of the country overran three of the insurgents' camps.
Boko Haram leader Abubakar Shekau said in a video earlier this month that the group had kidnapped several women and children in retaliation against security forces who, it says, detained the wives and children of its members without cause.
In their biggest offensive since the insurgency began in 2009, Nigerian forces are trying to chase well-armed militants out of territory they control in remote semi-deserts around Lake Chad, along the borders with Cameroon, Chad and Niger.
"Troops of the Special Operations have rescued three women and six children after overrunning three terrorists camps ... in the ongoing onslaught against terrorists," a statement from the defence ministry said on Saturday.
"Troops combing the forest are however yet to locate one other woman and her two children," it added.
President Goodluck Jonathan has declared a state of emergency in the three northeastern states. The operation has targeted areas of Africa's top energy producer where Boko Haram, which is fighting to create a breakaway Islamic state in religiously mixed Nigeria, has bases and weapons caches.
Retaking hostages was not one of the military's stated aims but the freeing of the hostages is some evidence of the progress the army says it has made against Boko Haram since launching the offensive 10 days ago.
Jonathan has also offered amnesty to Islamist insurgents who surrender and said he would release detained women and children linked to Boko Haram, one of the sect's chief demands.
An amnesty for militants in the oil-producing Niger Delta in 2009 helped end a conflict there that cut oil output by nearly half at one stage. But Boko Haram leader Abubakar Shekau rejected the offer of amnesty last month.
Boko Haram's four-year long insurgency has killed around 3,000 people and the group has become the biggest security threat to Africa's top oil exporter and second largest economy.