Russia is under further pressure over its unsupported claim of a “terrorist chemical attack” on Syria’s largest city Aleppo, with the US cautioning Moscow not to tamper with the site.

On Saturday, the Russian Defense Ministry and Assad regime asserted that rebels had fired mortars with chlorine on Aleppo. They posted video and photos of civilians with breathing difficulties, although none showed symptoms specific to inhalation of chlorine.

Russian State media initially said 12 people were killed, but later withdrew the headline and replaced it with more than 100 wounded. Photographs of the supposed attack show 120mm mortars — too small to carry the chlorine that would cause mass casualties.

Russian State outlet RT has retreated to a headline of “alleged chemical attack”, while falsely claiming “Western media is silent”. Syrian State news agency SANA has deleted its video of one of the claimed sites.

Syria Daily, Nov 27: Russia Scrambles Over “Terrorist Chemical Attack” Claim

The Organization for the Prohibition of Chemical Weapons, which has established chemical attacks by the Assad regime since 2014, has said it will investigate Saturday’s alleged assault.

Pentagon spokesman Cdr. Sean Robertson, pointing to previous Russian efforts to block blame of the Assad regime over sarin and chlorine attacks, said on Tuesday:

We caution Russia against tampering with another suspected chemical weapons attack site and urge Russia to secure the safety of the OPCW inspectors so these allegations can be investigated in a fair and transparent manner.

In April, residents and activists said Russian personnel removed evidence and disturbed the site of a chlorine attack by pro-Assad forces on Douma near Damascus. The regime allegedly delayed inspectors from reaching the site for days.

The attack on April 7 forced the surrender of the last opposition area near the Syrian capital a day later.

The Pentagon also called on the regime not to use “false pretexts” to attack the de-escalation zone around opposition-held territory in northwest Syria.

“We continue to engage the Russian government and military at senior levels to make clear that an offensive in Idlib would represent a reckless escalation of the conflict,” said Robertson.

Pro-Assad forces have shelled the periphery of the zone around Idlib and northern Hama Provinces, declared by Russia and Turkey on September 17.

On Sunday, Russia carried out its first airstrikes in 75 days on western and southern Aleppo Province, outside the zone, using the pretext of the “terrorist chemical attack” the previous day.

Russia, the regime, and their supporters have regularly put out unsupported assertions of preparations by “terrorists” and White Helmets rescuers for chemical attacks.