It was yet another missile, one of many fired by the Syrian regime at the rebel-controlled Jobar district of Damascus. But this one barely made a sound when it landed. Then, say witnesses, came the nausea.

“After the impact, people started fainting,” said Abbas, the nom de guerre of a 35-year-old opposition Syrian activist who lives nearby and saw the alleged aftermath of the September 10 attack. “There was no special colour in the air. But people started having breathing problems, big headaches.”

At least two people were reportedly killed and six contaminated win the attack, one of an increasing number in which the regime of Bashar al-Assad is alleged to be continuing to use toxic or chemical weapons in its war against an armed Sunni rebellion. […]