A massive explosion followed by a fire has hit near the international airport in Syria, activists say.
The chemical weapons watchdog OPCW says samples from 10 victims of the deadly attack were analysed.
A blast rips through buses carrying people from pro-government towns, waiting at a rebel checkpoint.
More than 30,000 people are expected to be moved from four towns under the deal.
Syria’s President Assad says reports of a chemical attack by his forces were “100% fabrication”.
G7 foreign ministers reject a UK drive for sanctions on Russia after the suspected chemical attack.
The US warns Syria not to use chemical weapons again, as G7 holds key talks in Italy.
The Kremlin was responsible “by proxy” as the “principal backer” of regime, says defence secretary.
The UK foreign secretary says his priority is to build international support for a ceasefire in Syria.