Human Rights Watch has appealed to the United States and other countries to halt all military aid to Egypt after a video of security forces apparently carrying out summary executions surfaced.
HRW said the Egyptian soldiers executed at least two people and as many as eight unarmed detainees in the country's Sinai region.
The he soldiers appeared trying to make the incident look as if they were engaged in clashes with fighters the group said.
Explaining that those killed had been arrested in Rafah last summer, Joe Stork, of HRW's Middle East section, said the group collected testimony that suggested security forces have been removing prisoners from detention centres and executing them.
"We have several testimonies of people being pulled out of detention for no reason that's clear to us, and they never get brought back to detention - and in some cases, like this one, they end up dead," Stork told Al Jazeera.
"The army and the security forces [claim] that this is the result of some sort of shoot-out between terrorists and security forces."
In the past, Egypt has claimed those killed were "terrorists" engaged in clashes with security forces in Sinai, where the army is battling a local affiliate of the Islamic State of Iraq and the Levant (ISIL) group.
Shot in the head
The video, which was posted online on Thursday by Mekameleen, an opposition TV channel based in Turkey, appears to show two blindfolded men being shot in the head by uniformed soldiers.
In the video, one young blindfolded man is aggressively questioned by the officers who ask him if he is a member of the Abu Sanana family.
When he responds "no" and says that he is from al-Awabadah, they ask him where his grandfather lives before forcing him to the ground and removing his blindfold.
One of the soldiers then shoots him in the head.
A person off-screen can be heard repeatedly shouting "Not just the head" as a second soldier then fires at the body on the ground.
Al Jazeera could not independently verify the video's authenticity. The Egyptian government has barred journalists from reporting on events in the Sinai Peninsula.
Possible war crimes
The leaked video appears to depict part of a raid that the Egyptian army posted on social media on December 6.
That post included photos of three men in a field with guns next to them, who had been "killed in a raid" on an explosives storehouse.
Ahmed Mefreh, a lawyer and human rights researcher, told Al Jazeera the killings amounted to war crimes.
"In the video, we see executions of unarmed people by forces wearing military uniforms," he said.
"They are being shot in a direct way. International law considers this a war crime that clearly has to be investigated."
Yehia Ghanem, Al Jazeera's Middle East analyst, said the names, villages and tribes mentioned by the victims lent authenticity to the video.
"It's important that the military call for an independent and impartial investigation in order to clear their name and reputation," he said.
"The political leadership needs to rein in the military. For the past few years they've been acting like a runaway train. Actions such as this endanger social peace in the region and could accelerate growing calls for Sinai to separate."
Last month, HRW accused Egyptian forces of executing at least four men in January 2017.
It said the killings appeared to fit a pattern of abuse against civilians by both military and internal security forces who have been deployed to Sinai.