It shattered the buses and set cars on fire, leaving a trail of bodies including children, as the convoy waited in rebel territory near Aleppo.
There were fears of revenge attacks on a convoy of evacuees from rebel-held towns, being moved under a deal.
But reports suggested both convoys have resumed their journey or would do soon.
The "Four Towns" deal brokered by Iran and Qatar was meant to relieve suffering in besieged towns - Foah and Kefraya in the north-west which were under government control, and rebel-held Madaya and Zabadani near Damascus.