A video purportedly showing an extrajudicial public beheading of two Bashar Assad loyalists has been uploaded onto the internet. Its authenticity has been verified by pro and anti-Assad sources, though it remains unclear who is behind the execution.

In the nine-minute clip, a group of several hundred people, including men, women and children stands around a hill, when the sentenced men, bound with ropes and wearing bags on their heads are led out. As the crowd closes in with shouts of Allah Akbar (“Glory to God!”) the two, who are wearing civilian clothes, are laid on the floor, and a bearded ‘executioner’ methodically saws through the throat of first one, then the other with a knife. The heads of the dead men are then placed on top of their bodies as the crowd continues to bay.

The phone-filmed video was uploaded on Wednesday to video-sharing site YouTube by Syrian Truth, a group that supports President Bashar Assad, which previously uncovered a clip of an anti-government fighter eating what appeared to be a human heart. According to the voices in the footage, it was shot in Khan al-Assal, near the city of Aleppo the north of the country.

The authenticity of the video was also endorsed by resources that have chiefly backed the rebels in the internal conflict that has lasted over two years – such as the UK-based Observatory for Human Rights and all4Syria.info, which moved to condemn its contents.

The identities of all parties involved in the video remain unclear.

A man is heard on the tape charges the two ‘convicted’ men of transporting weapons and ammunition for the regular army.

“I did not transport weapons, brother” cries out the man, writhing on the ground, with his hands tied behind his back.

One of the men in the video shouts out “This is punishment for the Shabiha!”. The Shabiha is a loyalist, semi-official plain-clothes militia that Assad’s opponents say has been used to crack down on dissent in contested areas. The force was implicated by the United Nations in the Houla Massacre last year, in which as many as a hundred people may have died.Various other media, sympathetic to Assad, claimed the men were Christians, executed for religious reason, with several alleging that one of those executed was a priest. No site supplied possible names of the condemned.

The identity of the executioners is also murky.

The Syrian National Coalition, which represents the mainstream opposition to Assad, said it was still running tests to verify whether the perpetrators were genuine rebel fighters, saying the sound and images may have been tampered with for propaganda purposes. It also insisted that the “rule of law” must be preserved, including the right of anyone captured to a “fair and free trial”.

The Syrian Observatory for Human Rights said on its Facebook page that “perpetrators spoke with a classical Arabic accent and did not sound Arabic, they sounded Chechniyan (sic)”. All4Syria also claimed the executioners were fighters from the former Soviet Union, possibly Uzbekistan or Azerbaijan. Snippets of Russian can be heard in the video.

Various local sources said the militia responsible may have been part of Jabhat al Nusra – the Al Qaeda-affiliated radical Islamist group that has swelled with foreign fighters and local recruits as the conflict has dragged on.

Videos of unconfirmed provenance, depicting atrocities and use of illegal weapons, have become an almost-daily feature of the war that has cost at least 90,000 lives according to the UN. An increasingly common aspect of the footage has been the disproportionate presence of often religiously-motivated paramilitary forces on both sides, as the culprits, suggesting that the conflict may have spiraled out of control of the main warring parties.