In one of the most disturbing allegations, Amnesty International says the Nigerian military executed more than 640 prisoners who briefly escaped during an attack by Boko Haram on a detention center in Giwa in March 2014.

Daniel Eyre from Amnesty says the man in command of operations that day was Major General Ahmadu Mohammed.

“He was also in charge of that military detention facility,” said Eyer. "And suspects on that facility died on an almost daily basis as a result of horrific conditions. They were tortured, starved, and even died of disease in that facility.”

Major General Ahmadu Mohammed was retired in 2014 for unrelated reasons, but Amnesty says he was reinstated last month.

In a report published last June, the group alleged that more than 7,000 detainees were starved, suffocated, and tortured to death in detention camps, and a further 1,200 were unlawfully killed.

A spokesperson for the Nigerian Ministry of Defense said Amnesty’s claims remain allegations unless they are proven beyond any reasonable doubt. Amnesty’s Daniel Eyre says the evidence is clear.

“Our report was based on interviews with more than 400 witnesses, including military sources,” said Eyer. "We also used video evidence of war crimes, including the execution of unarmed men by Nigerian soldiers.”

When the report was published in June, Nigerian President Muhammadu Buhari wrote on Twitter the allegations would be investigated.

“We are still waiting for those investigations, they have not begun yet; but, it is unthinkable that someone who was named in our report could be put in control of troops again, without those investigations having taken place,” said Eyer.

In recent days more than 150 people have been reported killed in Boko Haram attacks in Nigeria’s northeast. At least 65 people died when militants attacked civilians and set fire to houses in Maiduguri.