BEIRUT (AP) — The commandos infiltrated Syrian rebel-held territory near the Lebanese border, watching rebel fighters come and go from a two-story villa before slipping inside to plant a powerful bomb. The next morning, they detonated it as three rebel explosive experts and four assistants met inside, turning the villa to rubble in seconds.

The operation late last month in Syria’s western Qalamoun region was carried out by fighters from Lebanon’s militant Hezbollah group, several Lebanese officials close to the militants have told The Associated Press. The Shiite group has sent hundreds of its fighters into Syria to shore up President Bashar Assad’s overstretched troops, helping them gain ground around the capital, Damascus, and near the Lebanese border.