At least 20 people, including two women and four children, died Sunday in a new aerial bombardment in the city of Al Bab, in the northern province of Aleppo, the Syrian Human Rights Observatory reported.
The attack was carried out by helicopters belonging to the regime of President Bashar Al Assad, which dropped barrels filled with explosives into the town, killing a score of people and wounding dozens more.
The London-based Observatory and a wide network of activists in Syria did not rule out a rise in the fatality count due to the severity of the injuries some of the wounded sustained.
According to reports gathered by the group, victims are still buried under rubble in the town, but rescue efforts are under way.
In the same city, another 20 people died Saturday, including seven civilians - among whom were several children - in another air attack by the Syrian army.
Meanwhile, the Observatory also reported that heavy fighting between regime forces and the insurgents is continuing in the old portion of the city of Aleppo, and casualties have resulted on both sides.
In recent weeks, clashes between government forces and the rebels have intensified in Aleppo and its environs, where the military is attempting to regain positions it had abandoned.
More than 100,000 people have died since the outbreak of the conflict in Syria in March 2011, according to UN figures.