(Reuters) A Syrian rescue service operating in rebel-held territory said on Tuesday a helicopter dropped containers of toxic gas overnight on a town close to where a Russian military helicopter had been shot down hours earlier.

The opposition Syrian National Coalition (SNC) accused President Bashar al-Assad of being behind the attack. Assad has denied previous accusations of using chemical weapons.

A spokesman for the Syria Civil Defence said 33 people, mostly women and children, were affected by the gas, which they suspect was chlorine, in Saraqeb, in rebel-held Idlib province.

The group, which describes itself as a neutral band of search and rescue volunteers, posted a video on YouTube apparently showing a number of men struggling to breathe and being given oxygen masks by people in civil defence uniforms.

“Medium-sized barrels fell containing toxic gases. The Syrian Civil Defence was not able to determine the type of the gas,” said the spokesman.

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