Hundreds of people are dying in detention as Nigeria’s military cracks down on an Islamic uprising in the northeast, Amnesty International said on Tuesday. Some people are shot outright, some starve and others suffocate to death, it said.
The human rights group said some detainees died from suffocation in overcrowded cells, others from starvation and extra-judicial killings.
In Wednesday's report, it calls for an urgent investigation into the deaths.
There has not yet been an official response to the report.
But the Nigerian army has rejected all previous accusations of human rights abuses.
A senior Nigerian army officer told Amnesty that at least 950 people had died in military custody during the first half of this year, according to an advance copy of the report seen by the BBC.
Most had been accused of having links to the Islamist militant group Boko Haram, Amnesty said.
Boko Haram is fighting to overthrow Nigeria's government to create an Islamic state, and has launched a number of attacks on schools.
About 50 students were shot dead earlier this month in their hostel, in an attack blamed on Boko Haram.
A state of emergency was declared in three northern states in May - Yobe, Borno and Adamawa - in response to thousands of deaths in militant attacks.