LAGOS - Nigerian troops have rescued 338 people, almost all of them women and children, held by Boko Haram Islamists near the group's Sambisa forest stronghold in the restive northeast, the army said Wednesday.

"The (army) unit ... rescued 338 persons that were held captive by the terrorists," the army said of the Tuesday operation, adding that 192 of the survivors were children and 138 women.

The raid targeted "suspected Boko Haram terrorist camps at Bulajilin and Manawashe villages" on the edge of the Sambisa forest, the army said in a statement.

It said that troops killed 30 suspected jihadists and seized a cache of arms and ammunition in the area.

The statement also said four Boko Haram suspects on a suicide bombing mission to Gubula town in nearby Adamawa state were ambushed and killed by government troops.

Some weapons, unexploded ordnances, mortar bombs and some cash were recovered from the suspects, it said.

Boko Haram is believed to be holding more than 200 schoolgirls kidnapped in the northeastern town of Chibok in April 2014 in its stronghold in Sambisa forest. It was not clear whether any of the Chibok girls were among those rescued. The Nigerian military has in recent months claimed a string of successes against Boko Haram in its quest to end the hardline Islamist group's six-year insurgency.

Early August, the army claimed to have freed 178 people, including more than 100 children, held hostage by Boko Haram, following an operation near Aulari town, about 70 kilometres (40 miles) south of Maiduguri, the capital of Borno State.

The air force said in a statement on Tuesday it had launched strikes on the group's vehicle and fuel depots "in a renewed drive to further degrade" its assets.

Air force chief Sadique Abubakar was quoted as saying the strikes were helping "pave the way for the final onslaught" by Nigerian ground forces.

President Muhammadu Buhari, who came to power in May on a pledge to crush Boko Haram, has given his military commanders until the end of December to defeat the group.

The Boko Haram violence has killed at least 17,000 people and forced more than 2.5 million to flee their homes since 2009.

But the hardline sect has stepped up its bomb and suicide attacks on so-called "soft" civilian targets such as markets, mosques, churches and bus stations in recent months.

Nearly 170 people have been killed this month and more than 1,420 since Buhari came to power, according to an AFP tally.

Boko Haram has also carried out cross-border attacks in Cameroon, Chad and Niger.

A multi-national regional force from Nigeria, Cameroon, Chad, Niger and Benin is trying to deploy to fight the insurgents.