A video has emerged that allegedly shows Egyptian soldiers shooting dead unarmed detainees in the northern Sinai region, where the military is carrying out an anti-terror offensive.
The footage, which is unverified, appears to show military officers rearranging the scene to make it seem as if a gun battle had taken place.
Soldiers are shown apparently placing weapons beside the dead bodies.
A pro-government news site has said that the 2016 video is a fabrication.
So far there has been no comment from the Egyptian military, which has previously released footage - apparently from the same incident late last year - saying it had eliminated a "dangerous terrorist cell" after a heavy exchange of gunfire.
Human rights group Amnesty International said it had analysed the footage. It showed "cold blooded killings", which it said should be urgently investigated by the Egyptian authorities.
The footage, which emerged on Thursday, was apparently filmed with a mobile phone and has been broadcast on Mekameleen TV, a station that supports the outlawed Muslim Brotherhood.
It appears to show two detainees being shot at point-blank range by Egyptian soldiers.
One man is already on the ground when he is shot four times. Later, a rifle has appeared by his side.
A younger man, who appears to be unarmed, is blindfolded and briefly interrogated before apparently being shot dead.
Egypt's army has, for years, been carrying out an offensive against Islamist militants in the northern Sinai peninsula, where an affiliate of so-called Islamic State (IS) is active.
However, Najia Bounaim, Amnesty International's campaigns director for North Africa, said there had also been a "disturbing pattern" of apparent extrajudicial executions in the area.
The organisation is also calling for an investigation into the deaths of six men, who were allegedly killed in police custody in North Sinai in January.
Earlier this month, President Abdul Fattah al-Sisi ordered military deployments across Egypt after dozens of people were killed in two blasts targeting Coptic Christians on Palm Sunday.
IS said it was behind the explosions.
Last month, 10 Egyptian soldiers were killed by two roadside bomb blasts during a raid against jihadist militants in the Sinai peninsula, according to military officials.
In February, five soldiers were reportedly killed by a roadside bomb in north Sinai.
President Sisi ordered military and police chiefs "to completely eradicate terrorism in northern Sinai and defeat any attempts to target civilians or to undermine the unity of the national fabric" in response to February's killings.