The Nigerian army has freed 178 people held hostage by the Islamist group Boko Haram in Borno state, the nucleus of the armed insurgency.

More than 100 of the rescued hostages were children, said an email statement issued by army spokesperson Colonel Tukur Gusau.

Scores of militant camps were also cleared in the town of Bama as part of the offensive against Boko Haram.

The spokesperson added: "In addition, one Boko Haram terrorist commander was captured alive and is presently undergoing investigation."

"Also, three Boko Haram flags were recovered while five motorcycles were burnt by the troops. The troops' morale remains high as they are determined to consolidate on the success achieved so far under Operation LAFIYA DOLE."

The army did not say whether any of the freed captives belonged to the group of Chibok students kidnapped in April 2014.

Airstrikes provided cover to the ground forces during the operation.

Boko Haram, meaning "Western education is prohibited", has been engaged in an armed insurgency against the African nation for the past six years with an aim to carve out a separate Islamic state under harsh Shariah law. Since 2012, more than 15,000 people are estimated to have been killed in bloody attacks with nearly a million people forced to flee.

Nigeria's fresh drive against Boko Haram has come at a time when African nations are bracing to step up their offensive against the militants.

Over the weekend, Benin, Nigeria's neighbour, pledged to dispatch 800 troops to join the African regional force drafted in by Nigeria, Chad, Niger, and Cameroon to combat Boko Haram militancy.

"This is an opportunity for Benin to express solidarity with countries on the front line against the Islamic sect, Boko Haram. This solidarity will result in the sending of 800 men from Benin's army," the country's President Thomas Boni Yayi said in a statement.