The right group, Amnesty International has disclosed that an elite police unit in Nigeria has subjected people to hangings, mock executions and starvation to force them to confess to crimes or to solicit bribes.
In statement on Wednesday, the leading right group said the special anti-robbery squad holds detainees in several facilities near Abuja, including one known as The Abbatoir, it adds.
Nigerian police have not yet commented on the report.
Amnesty quoted a 25-year-old unnamed fuel attendant from Onitsha, Anambra State as saying he was arrested by the squad after being accused of a burglary.
Recalling his detention he said:
“The policemen asked me to sign a plain sheet. When I signed it, they told me I have signed my death warrant. They left me hanging on a suspended iron rod. My body ceased to function. I lost consciousness. When I was about to die they took me down and poured water on me to revive me."
Amnesty quoted another man, Chidi Oluchi, as saying he was arrested in Enugu State before being robbed of his belongings and tortured in custody by police officers officers.
“They told me to slap myself and, when I refused, they started beating me with the side of their machetes and heavy sticks. My mouth was bleeding and my vision became blurred.”
Mr Oluchi told Amnesty he was released after paying officers a bribe of $100 (£77).