A number of prominent human rights groups appealed to the United Nations on Monday to open an investigation into the massacre.
The groups urged , US envoy to the UN, to look into the , in which 41 civilians were killed by Syrian regime forces in the Tadamon neighbourhood of Damascus in April 2013.
"We are writing to demand immediate action to address this massacre, which amounts to a war crime, and hold perpetrators accountable at the UN Security Council," the letter, issued by the (SNHR), read.
The SNHR also appealed to the US to hold a meeting at the during its presidency in May and launch an independent inquiry into the case.
The appeal comes two weeks after the Guardian newspaper published a report that included leaked video footage purportedly showing evidence of committed against civilians by Syrian forces.
The footage showed blindfolded and handcuffed civilians being instructed to run towards an execution pit located in front of them in the Tadamon district. The footage also shows members of the infamous Branch 227 appearing amused as they the civilians, after which they doused gasoline on the bodies and set them alight.
"Never before have we seen such clear evidence of a war crime committed and videotaped by Assad’s intelligence services in broad daylight, , with no regard for the humanity of the victims or concern for consequences," the SNHR continued in the letter.
The video triggered a public outcry from Syrians, with some families recognising relatives being executed in the footage.
The civil society groups have also decried the lack of response from the international community, particularly in the context of committed by Russian forces in Ukraine.
"It's high time that the international community learned that impunity for grave human rights violations in Syria has far-reaching consequences beyond its borders," they concluded.
Rights groups estimate that around 500,000 people have in the Syrian conflict since its onset in 2011. Advocacy groups also state that scores of Syrians remain displaced and missing, including children.