BEIRUT (AP) — Syrian rebels fired at tanks in Damascus residential districts, armored vehicles blocked the main entrances to a neighborhood and protesters briefly barricaded a main highway into the city with bricks and burning tires, leaving hundreds of cars backed up in some of the worst clashes to hit the tightly controlled capital since the uprising began 16 months ago.

The scenes from the second straight day of fierce clashes in Damascus, unfolding in amateur videos posted online, were the latest evidence that Syria's conflict is fast devolving into a civil war that is moving ever closer to the seat of President Bashar Assad's power.

Plumes of black smoke drifted over the city skyline and gunfire could be heard throughout the capital, even in the upscale cafes in downtown frequented by members of Assad's regime. The fighting left many streets deserted in a string of neighborhoods on the city's southwest corner where the fighting was focused. Many families have fled, and fear grips many who remain behind.