The United Nations envoy for Syria has voiced deep concern about civilians in the city of Zabadani, Al Arabiya news channel reported on Wednesday.

Staffan de Mistura said the military had dropped a large number of barrel bombs on Zabadani “causing unprecedented levels of destruction and many deaths among the civilian population.”

The Syrian air force has bombarded areas in and around the city and Sunni insurgents have retaliated by firing rockets and heavy mortar shells on two villages near Idlib city in the north, de Mistura said.