The Nigerian army is moving in to Boko Haram's final stronghold in the Sambisa forest to rescue more than 200 Chibok schoolgirls after one managed to flee the jihadists who have held them for over two years, a provincial governor said on Thursday.

Shortly after escapee Amina Ali Darsha Nkeki met Nigerian President Muhammadu Buhari, the governor of Borno state where the town of Chibok is located said army generals were already drawing up plans to rescue her classmates.

"We believe that in the coming weeks we shall recover the rest of the girls," Governor Kashim Shettima told reporters. "The military is already moving into the forest."

Previous military attempts to storm Sambisa have met with mixed success, with soldiers making significant in-roads but failing to finish off Boko Haram after running into bands of well-armed guerrillas, mines and booby traps.

After Amina was discovered on Tuesday by soldiers and a civilian vigilante group, the army said it had detained a suspected Boko Haram militant called Mohammed Hayatu, who said he was Amina's husband.