"A truck packed with explosives detonated... Near a branch of the military intelligence, killing at least five people and injuring more than 20," the Syrian Observatory for Human Rights said.
Syrian state television also reported the blast, saying four people had been killed and 22 wounded in a "terrorist explosion" at the southern entrance of the city.
In the northern province of Raqa, two suicide bombers exploded inside base 17, an army base under siege by opposition forces, according to the Observatory, a Britain-based group that relies on activists and other witnesses inside Syria.
Clashes between regime forces and ISIL broke out after the blasts, which the Observatory said killed several soldiers.
More From This Section
In Damascus meanwhile, the group said a man died after regime shelling a day earlier on the Palestinian Yarmuk camp, where a ceasefire has broken down.
The renewed fighting has halted aid delivery efforts to the besieged camp, where two more people died from lack of food and medical care yesterday, the Observatory said.
More than 140,000 people are estimated to have been killed since the start of the uprising against President Bashar al-Assad in March 2011.