There is a high concentration of foreign fighters in Syria's Idlib province, including an estimated 10,000 terrorists, UN Syria envoy Staffan de Mistura told reporters on Thursday. The diplomat said it would be better to set up humanitarian corridors to evacuate civilians than rush into a battle. The envoy called on Russia, Iran and Turkey to forestall a battle in Idlib which would affect millions of civilians and “could see both sides using chlorine as a chemical weapon,” Reuters reported. Russian Foreign Ministry spokeswoman Maria Zakharova said on Thursday that terrorists have reportedly brought containers with chlorine to the town of Jisr al-Shughur for the staging of a chemical attack, which is sure to be blamed on Syrian government troops, TASS reports. “According to the information available, eight containers with chlorine and ammunition for a multiple launch rocket system to be filled with this chlorine were delivered on August 23 and 24 in the area of the Idlib de-escalation zone,” she said.