Many civilians were injured in the raid by Assad's air force on Azaz, according to Doctor Mohammad Lakhini at the town's hospital.
Many houses were destroyed and dozens of men made their way out of the concrete and metal debris, searching for survivors in the northern Syrian town.
Doctors at the hospital were forced to close their doors and direct people to the nearby border with Turkey.
In video posted by activists, residents in Azaz, which is near the Turkish border, called out "God is greatest" as they carried wounded bodies from the debris.
The opposition Syrian Observatory for Human Rights said more than forty people had been killed. One activist in Azaz said at least 30 bodies had been found and rescuers were searching for more.