Amman: Syrian jets resumed strikes on several rebel-held towns in southern Dera’a province on Tuesday, rebels said, a day after Washington warned that such bombing would violate a US-Russian “de-escalation zone”.

Two rebel sources said jets bombed the towns of Hrak, Busr Al Harir and a location in Laja, all places which were hit on Monday, the first air strikes since a US-Russian agreement brokered last July on the de-escalation zone in southern Syria.

Several rebel sources had said some preparations were underway for such a military campaign as popular pressure in rebel-held areas mounts on the factions to attack the Syrian army, which has been sending reinforcements from the south to Eastern Ghouta.

Meanwhile, sick and injured civilians left a rebel enclave in Syria’s Eastern Ghouta on Tuesday under the first medical evacuation since a massive assault began nearly a month ago.

Women carrying infants, men hobbling on crutches and an old man in a wheelchair waited at a school nearby, along with dozens who exited through the Al Wafideen crossing, a witness said.

During the regime’s offensive, more than 1,100 civilians have died in the last big rebel bastion near the capital, the UN office of humanitarian affairs says.