Fierce clashes between Syrian government forces and opposition fighters in the country’s south killed dozens on both sides over the past two days as rebel factions regained much of the ground they lost earlier, activists said Tuesday.

The Britain-based Syrian Observatory for Human Rights said the fighting, which began Monday in the southern province of Daraa, killed 37 rebels as well as 22 government troops. On Tuesday, the Syrian air force struck several areas in Daraa province, the Observatory said.

The Local Coordination Committees, another activist group that tracks the Syrian civil war, said the violence in Daraa left at least 27 people dead on Monday alone.