Nigerian warplanes bombarded training camps and caches of weapons and vehicles belonging to the Islamist group Boko Haram in the northeasterly Samibisa forest on Thursday, the military said.

"The death of a large number of terrorists has been recorded while many others are also scampering all over the forest and out of the struck bases," defense spokesman Major-General Chris Olukolade said.

After a year in which Boko Haram seemed to be gaining ground, seizing swathes of territory, killing thousands of people and kidnapping hundreds of mostly women and children, the tide has appeared to turn against them in the past month, as neighboring countries plagued by cross-border attacks have weighed in.

Nigerian forces have killed more than 300 Boko Haram fighters during an operation to recapture 11 towns and villages since the start of the week, the military said on Wednesday, though it was not possible to independently verify this and the military has in the past been accused of exaggerating enemy casualties while understating its own.

Samibisa gained notoriety last year when more than 200 girls kidnapped by Boko Haram from a secondary school in nearby Chibok were taken there. Some of them escaped Samibisa shortly afterwards but most have remained in captivity ever since.

Aerial surveillance of the forest has not revealed their whereabouts.