BEIRUT (AP) — Syrian rebels fired grenades at tanks and troops while regime armor shelled Damascus neighborhoods on Monday, sending terrified families fleeing the most sustained and widespread fighting in the capital since the start of the uprising 16 months ago.

A ring of fierce clashes nearly encircled the heavily guarded capital as rebels seeking to overthrow President Bashar Assad pushed the civil war that has been building in Syria’s impoverished provinces closer to the seat of power.