The Nigerian military was given up to four hours' advance notice of the Boko Haram attack on the boarding school in Chibok from where more than 200 schoolgirls were kidnapped, according to sources independently verified by Al Jazeera and Amnesty International.
Two politicians from Nigeria's northeast Borno state told Al Jazeera's Yvonne Ndege that security forces had been given at least two hours' warning of an attack on the town, but failed to act.
Makmid Kamara, the Nigeria researcher for Amnesty International, said Amnesty had been told the military had four hours' advance warning.
Al Jazeera's Yvonne Ndege reports from Abuja.
