Amnesty International on Thursday said Azerbaijan and Armenia must urgently probe "war crimes" committed by both sides during recent fighting over disputed territory of Nagorno-Karabakh.
Azerbaijan and Armenia last month signed a Moscow-brokered peace deal ending six weeks of brutal conflict over the breakaway region after Baku's army overwhelmed separatist forces.
Both sides have accused each other of violating international law during the war.
Amnesty said it had analysed 22 videos depicting "extrajudicial executions, the mistreatment of prisoners of war and other captives, and desecration of the dead bodies of enemy soldiers".
The rights group said it had verified 12 videos showing abuses by Armenian forces and 10 involving Azerbaijani troops.
One video analysed by Amnesty shows two men wearing Azerbaijani military uniforms holding down an elderly man who begs for his life as one of the men cuts his throat.
In another, a gagged and bound man wearing an Azerbaijani border patrol uniform lies on the ground as a man speaking to him in Armenian sticks a knife into his throat.
"The depravity and lack of humanity captured in these videos shows the deliberate intention to cause ultimate harm and humiliation to victims, in clear violation of international humanitarian law," said Denis Krivosheev, Amnesty International's research director for Eastern Europe and Central Asia.
"Both Azerbaijani and Armenian authorities must immediately conduct independent, impartial investigations and identify all those responsible," he said.
The rights group said it had authenticated the videos as genuine and that a forensic pathologist had verified the details of the injuries.
The fierce clashes that broke out over the mountainous Karabakh region in late September left more than 5,000 people dead, including civilians.
On Wednesday, Azerbaijan and Armenia accused each other of using weapons containing white phosphorus during the fighting.
The use of phosphorus as a chemical weapon is prohibited under international law, but it is allowed to illuminate battlefields and be used as a smokescreen.
