Footage shot by a Reuters crew in the Syrian city of Harem appears to show opposition fighters gunning down an unarmed man in the street.
The footage shows three opposition fighters firing at an unarmed man who is cornered against a wall. The rebels fire multiple times until the man stumbles to the ground, and shoot him once more after he falls to the floor.
In the next scene, fighters surround a a bearded man who is lying on the pavement, covered in blood. "Kill me, kill me," he says. The rebels refuse.
A third sequence shows several bodies lying lifeless in a building in the neighborhood. Four bodies stacked on top of one other appear to have been shot in the head.
Reuters reports that opposition fighters had surrounded Harem, a neighborhood near Aleppo, last week and went house by house searching for people who they believed to be loyal to the regime of embattled Syrian president Bashar Assad.
From one building they hauled a man in middle age, dressed in casual clothes, black bearded and without a weapon. He seemed anxious and shied away as he stumbled into the street. Three rebels fighters casually raised their Kalashnikov rifles. A shot rang out, then another. A third. The man began to fall. Still silent. More shots. He lay still. A final round hit his head.
In response to the video, the Syrian National Council, an opposition group, told Al Jazeera that it condemns all human rights violations but that it remains unclear if the opposition fighters in the video are members of the Free Syrian Army.
Last week, another disturbing video emerged, purporting to show Syrian rebel fighters executing a group of captured, terrified government soldiers.
According to the United Nations, the Syrian regime is to blame for most of the war crimes that have occurred during the conflict, but offenses by rebels are on the rise. "The balance is changing somewhat," Karen Abu Zayd, a member of the U.N. panel documenting war crimes in Syria, told the Associated Press.
At this stage "there may not be anybody with entirely clean hands," Amnesty International's Suzanne Nossel added.
More than 35,000 people have been killed since the start of the conflict in Syria in March 2011, activists estimate. On Friday, at least 9,000 Syrians crossed into Turkey to flee from the violence.