BEIRUT (AP) — Tens of thousands of terrified men, women and children streamed out on foot and in pick-up trucks Thursday from besieged enclaves on two fronts, fleeing bombings from the Syrian military near the capital, Damascus, and Turkish troops in the country's north.

It was the largest single-day exodus of civilians from fighting in Syria's civil war and a reminder of how the conflict that sparked the world's worst humanitarian catastrophe continues to hit new lows as it enters its eighth year.

The flight of an estimated 42,000 civilians came as their attackers— Syrian government troops, b...