More than 7,000 men and boys have died in Nigerian military custody during its fight against Boko Haram over the last four years, Amnesty International says.
They are among more than 20,000 people who have been arrested during operations against the Islamist militants, the rights group says.
The military has rejected the allegations, calling the report biased and the statistics "spurious".
More than 15,500 people have been killed during the insurgency.
About 1.5 million people have also been displaced and hundreds more abducted since Boko Haram launched its violent uprising to impose Islamic rule in 2009.
'Deliberately starved'BBC Nigeria correspondent Will Ross says Amnesty International and other human rights groups have accused Nigeria's security forces of carrying out many atrocities before.
But this report goes further as the UK-based rights group names several senior officers - including major generals and brigadier generals - and calls on them to be investigated for murder, torture and enforced disappearance, he says.(http://ichef.bbci.co.uk/news/200/media/images/75306000/jpg/_75306515_line976.jpg)(http://ichef.bbci.co.uk/news/200/media/images/83392000/jpg/_83392848_cef782fa-ed96-4543-81db-74fd1bf83410.jpg)Africa news updates (http://www.bbc.co.uk/news/live/world-africa-32947745)(http://ichef.bbci.co.uk/news/200/media/images/75306000/jpg/_75306515_line976.jpg)In response, military spokesman Maj Gen Chris Olukolade said the report "went out to gather names of specified senior officers, in a calculated attempt to rubbish their reputation".
The report, entitled Stars on their shoulders, Blood on their hands, says (https://www.amnesty.org/en/articles/news/2015/06/Nigeria-Senior-members-of-military-must-be-investigated-for-war-crimes/) the senior officers should either be investigated for carrying out the war crimes themselves or for being in command of subordinates who did so.
Amnesty International says more than 1,000 people have been unlawfully killed.
It says in some cases captives were deliberately starved in custody and boys as young as nine years old have been detained.
The human rights group calls on Nigeria's new President Muhammadu Buhari to end the culture of impunity in the armed forces.
At his inauguration last week, Mr Buhari promised (http://mbuhari.ng/full-text-of-the-inaugural-speech-of-president-muhammadu-buhari/) to "overhaul the rules of engagement to avoid human rights violations in operations".
This year Nigeria's army - backed by regional forces - has recaptured many towns and villages from the militants.
But the group is still holding many women, girls and children captive, including 219 schools girls it kidnapped from a school in Chibok in April last year.
Source: BBC