The Syrian government of President Bashar Al-Assad was behind a chemical attack in Aleppo last month, despite accusing the opposition of being the perpetrator, an assessment by US intelligence has revealed.

In newly declassified documents released by America yesterday, the Syrian government is accused of leading a false flag operation to throw suspicion on the opposition, a charge fiercely denied by faction leaders, who stated that no group had the ability to produce chemical weapons.

Shelling of a toxic substance wounded more than 100 people in a suspected toxic gas attack in Aleppo at the end of November, which a health official described as the first such assault in the city. It marked the highest such casualty toll in the city since it was besieged and recaptured by government forces two years ago.

The chemical used in the attack was revealed to be tear gas, rather than chlorine that was first suspected. The documents stated that “technical analysis of videos and images of munition remnants of Russian-media portrayed mortars indicate they are not suitable for delivering chlorine” and that witnesses describe the characteristic odour of chlorine bombs.

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Since the attack, the regime has maintained control over the site, prompting concern that Syrian forces could contaminate the site or fabricate samples to hand over to the Organisation for the Prohibition of Chemical Weapons (OPCW).

Last week the Russian Foreign Ministry denounced any position the US would take on the attacks, claiming that its stance on the matter was “preconceived”.

Investigations by the OPCW have found evidence that the Syrian regime has repeatedly gassed civilians with chemical weapons, offences that constitute a war crime and are prohibited under the Chemical Weapons Convention. There have been some 33 uses of chlorine weapons attributed to the government, with several other chemicals also used.

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