A rescue service operating in rebel-held territory in Syria says containers of gas have been dropped from the skies onto the town of Saraqeb, in Idlib province.
Saraqeb is close to the place where a Russian military helicopter was shot down on Monday, killing all five people on board.
Meanwhile, US-backed Kurdish-led fighters say they now control nearly three quarters of a strategic city in northern Syria, that was a Daesh stronghold.
Fierce combat has raged for two months, with thousands of residents said to be trapped inside Manbij.
Its loss would be a huge blow to Daesh which has used the city as a transit point for foreign fighters and provisions from the Turkish border.
Manbij is in the northern province of Aleppo, which forms a theatre for several separate battles between multiple warring sides in Syria’s five-year-old conflict.
Editor's note: This article has been edited from the source material.
