“Civilians are paying a heavy price as the cycle of violations and reprisals gather momentum.”

At least 1500 people, more than half of who are civilians, have been killed in the first three months of 2014 alone following an upsurge of the conflict in the northeast of Nigeria, Amnesty International (AI) has said.

In a report published on Monday, the global human rights organisation said many killed are victims of the terrorist group, Boko Haram and “uncontrolled reprisals” by the country’s security forces.

In the light of this revelation, AI is asking for independent investigations into what it said may constitute war crimes and crimes against humanity.

“More than 1,500 deaths in three months indicate an alarming deterioration in the situation. The international community cannot continue to look the other way in the face of extrajudicial executions, attacks on civilians and other crimes under international law being committed on a mass scale. Civilians are paying a heavy price as the cycle of violations and reprisals gather momentum,” said Research and Advocacy Director for Africa at Amnesty International, Netsanet Belay.

The organisation particularly mentioned the incident of March 14 when Boko Haram fighters attacked Giwa Barracks in Maiduguri to free their fighters imprisoned in the military facility. AI said the military “unleashed a brutal crackdown on former detainees as they tried to flee after being freed by the gunmen.”

Relying on witness, lawyers, human rights campaigners, and hospital staff accounts from across the city, AI said soldiers as well as members of the vigilante group, Civilian JTF, rounded up unarmed former detainees and summarily executed them. It also said it is in possession of satellite images that show possible mass graves.

“The scale of atrocities carried out by Boko Haram is truly shocking creating a climate of fear and insecurity. But this cannot be used to justify the brutality of the response that is clearly being meted out by the Nigerian security forces,” said Mr. Belay.

“The former detainees were in a classroom. They started screaming ‘we are not Boko Haram. We are detainees!’ My neighbours and I saw the soldiers take the men to a place called ‘no man’s land,’ behind the University of Maiduguri. We watched as the soldiers opened fire killing all 56. They were killed in front of us. All of them,” an unnamed witness told AI.

Another witness at the Jiddari Polo area of the city told Amnesty International that the Civilian JTF rounded up more than 190 fleeing detainees and handed them over to the soldiers who proceeded to shoot them.

“I saw the soldiers asking the people to lie on the ground. There was a small argument between the soldiers and the civilian JTF. The soldiers made some calls and a few minutes later they started shooting the people on the ground. I counted 198 people killed at that checkpoint,” the witness said.

Following the unwillingness of the Nigerian authorities to investigate allegations of extra-judicial killings, AI called on Economic Community of West African States (ECOWAS), the African Union and United Nations to investigate these accusations.

“The summary killing of these detainees amount to extrajudicial executions and are crimes under international law. These killings follow an entrenched pattern of deaths in custody of detainees held in relation to the situation in the northeast,” said Mr. Belay.

“The international community, and in particular the African Commission on Human and People’s Rights and the UN Human Rights Council, must, as a matter of urgency, ensure that a thorough, impartial and transparent investigation is conducted into these allegations of war crimes and crimes against humanity in Nigeria.”

This is not the first time AI or other rights organisations will call for investigations into alleged extrajudicial and the indiscriminate killing of civilians by Boko Haram and the Nigerian military. Human Rights Watch and other rights groups had published detailed reports of the killings and destruction of property of those suspected of being members of Boko Haram by the military.

The Nigerian government has always cleared the military of any blame.