The Nigerian army has freed 178 people being held hostage by Boko Haram jihadists including more than 100 children, it said late Sunday, as it carries out a regional offensive aimed at rooting out the insurgency.

"During the offensive operations, 178 people held captives by the terrorists were rescued, they include 101 children, 67 women and 10 men respectively," army spokesman Colonel Tukur Gusau said in a statement.

The rescue took place near Aulari about 70 kilometres (40 miles) south of Maiduguri, the biggest town in northeast Nigeria, he said, without specifying when the operation was conducted.

"In addition, one Boko Haram terrorists commander was captured alive and is presently undergoing investigation," the spokesman said.

The Nigerian military has announced the release of hundreds of people held captive by Boko Haram in recent months, especially in the notorious Sambisa forest, a longtime Islamist stronghold now affiliated with the Islamic State group.

Last week, the army said it had released 30 hostages including 21 children about 90 kilometres east of Maiduguri, and 59 captives in another operation near the town of Konduga in the same area.

Earlier Sunday the Nigerian military said it had conducted air strikes on the village of Bita, not far from the Sambisa forest, where Boko Haram was preparing to launch an offensive. "Many" Islamists were killed, the military said, without elaborating.

Boko Haram's bloody insurgency in Nigeria alone has left more than 15,000 people dead since 2009. In recent months, the group has increasingly expanded its operations into neighbouring countries.