Over 7,000 males have died while in custody of the Nigerian military over the last four years, Amnesty International has revealed in a new report.
Over 20,000 people are said to have been arrested in operations against Boko Haram militants, the UK-based rights group said.
Nigeria's military has rejected the allegations, calling the report biased and the statistics "spurious".
The report, entitled Stars on their shoulders, Blood on their hands, names several senior officers and calls for investigations into their role in murder, torture and enforced disappearances.
“This sickening evidence exposes how thousands of young men and boys have been arbitrarily arrested and deliberately killed or left to die in detention in the most horrific conditions. It provides strong grounds for investigations into the possible criminal responsibility of members of the military, including those at the highest levels,” said Salil Shetty, Amnesty International’s Secretary General.