DHAKA: 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, Al-Jazeera reported.

This is a shocking revelation.

Makmid Kamara, Nigeria researcher, Amnesty International

Makmid Kamara, the Nigeria researcher for Amnesty International, said Amnesty had been told the military had at least four hours' advance warning.

The schoolgirls remain missing after being abducted on April 14, more than three weeks ago. The Nigerian government's slow response to the abduction has led to protests around the country.

"We received information and we spoke to a senior Nigerian military officer, who spoke to us on condition of anonymity, that they had received intelligence reports, even before local authorities and politicians got the information, that gunmen were on their way to the Chibok town," Kamara said.

Kamara told Al Jazeera that senior officials in Maiduguri and Dambua towns were alerted around 7pm on April 14, and that information was relayed to the senior military officers based in Dambua and Maiduguri.

"Later on, at 10pm on the same night of the 14th of April, local authorities, who Amnesty had spoken to, informed us, that they informed the local military command in Chibok town about the planned attack," Kamara said.

"When I spoke to one of the senior military officials, they informed me that they [had] informed their superiors, and requested for reinforcement. But the reinforcement did not come."

BDST: 0950HRS, MAY 10, 2014