Paris - Amnesty International said on Tuesday that soldiers loyal to Mali's ousted government had been tortured and suffered other rights abuses at the hands of the junta behind a March coup.
The soldiers either disappeared or suffered summary executions and torture when they were detained after taking part in a 30 April counter-coup, the rights body said in a report issued in French on Tuesday.
Once one of the region's stable democracies, the landlocked west African nation crumbled into despair in half a year as a Tuareg rebellion sparked a coup which allowed jihadists to seize more than half of its territory.
A junta led by Captain Amadou Sanogo ousted the regime of Amadou Toumani Toure on 22 March, handing power to a civilian transition government, with interim President Dioncounda Traore appointed in April.
The Amnesty report, which comes after a 10-day fact-finding mission to the country in July, contains accounts of abuses "committed by soldiers loyal to the military junta against soldiers and police officers linked" to the counter-coup.
The rights body called on Mali officials to put an end to the "vicious cycle of human rights violations" and to launch a probe into "the dozens of cases of forced disappearances, extrajudicial executions and torture" of which it is aware.
The call comes as Traore faces Tuesday a deadline set by the Economic Community of West African States (Ecowas) to form a unity government, which is expected to be better able to deal with the occupation of the north by hardline Islamists.
Amnesty members spoke to 50 people detained at an official detention centre who had previously been detained "in appalling conditions" at the Kati military camp.
The prisoners said they witnessed 21 people disappear "after being removed from their cells in the night from May 2 to 3".
They also described "the inhuman and degrading conditions" of their detention, as well as the torture and sexual acts to which they were subject.
One prisoner quoted in the Amnesty report said, "They made us lie face down and handcuffed our hands behind our backs and linked them to our feet."
"One of the soldiers used a baton to shove a cloth down our mouths. We could no longer speak, much less scream," he continued.
"They put out cigarettes on our bodies and one of them put one out in my left ear."
A police officer also said he and three other prisoners were forced to sodomise each other under threat of execution.
Amnesty added that "Mali's transition government had failed to protect the human rights of its citizens and this absence of law cannot continue".
It asked the Mali courts to open an immediate investigation into "these very serious events and restore stability in a country that has suffered enormously in the last six months".