LAGOS, Nigeria (AP) — Nigeria's military has killed at least 150 peaceful protesters in a "chilling campaign" to repress renewed demands to create a breakaway state of Biafra in the southeast, Amnesty International said Thursday.

The military denied any "killing of defenseless agitators." Security forces have "exercised maximum restraint" in response to violent protesters who in May killed five police officers and wounded several soldiers, said army spokesman Col. Sani Kukasheka Usman.

The London-based human rights organization said an analysis of 87 videos, 122 photographs and testimony from 146 witnesses showed "the military fired live ammunition with little or no warning" into crowds protesting in several cities between August 2015 and August 2016.

Hundreds of people have been arbitrarily detained and some tortured, Amnesty said.

The report quotes one woman in Onitsha city who said her husband called her May 30 to say a soldier had shot him in the stomach and he was in a military truck with six others, four already dead, and then whispering that the vehicle had stopped. Then she heard gunshots. The woman later found her husband's body at a mortuary with three gunshot wounds, one to the stomach and two in the chest, the report said.

Amnesty said it has "evidence of mass extrajudicial executions by security forces," including at least 60 people killed at a May 30 rally in Onitsha to commemorate the 1967-1970 civil war to create a Biafran state for the Igbo people. One million people died in that war.

Usman accused the secessionists of targeting other tribes in "a reign of hate, terror and ethno-religious controversies ... (threatening) national security."

Protests have increased, along with military violence, since the October 2015 arrest of Nnamdi Kanu, a leader of the Indigenous People of Biafra, who has broadcast incendiary statements in southeast Nigeria through the group's London-based clandestine Radio Biafra.

Amnesty said that Nigeria's President Muhammadu Buhari has promised to investigate but done nothing about its previous reports documenting the December 2015 military killings of more than 300 Shiites and the deaths in military detention of some 8,000 people in the war to curb Boko Haram's Islamic.