An explosion late on Friday on the outskirts of the town of Sweida killed Sheikh Wahid al-Balous, a leader of the minority Druze community in Syria who opposed both the Syrian government and Islamist insurgents fighting against it, the British-based Syrian Observatory for Human Rights said.
Another car bomb went off at around the same time in Sweida and both explosions killed 26 people in total, the Observatory said.
Syrian state television confirmed the two blasts and the toll, blaming the explosions on insurgents. It did not mention the Druze leader.
There was no immediate claim of responsibility for the attacks.
Insurgents including the Nusra Front and Islamic State have been trying to advance toward Sweida province, a Druze stronghold.
After the attack, dozens of people protested outside government buildings in the Sweida area, setting cars alight and destroying a statue in the town of former President Hafez al-Assad, father of President Bashar al-Assad, the Observatory said.
Calm had returned to the area on Saturday morning, according to the Observatory, which tracks the Syrian civil war using contacts on the ground.