"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 on Thursday.
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 province of Raqa, two suicide bombers also blow themselves inside base 17, an army base under siege by foreign-backed militants, to kill Syrian soldiers.
According to the report, both terrorists from the extremist Islamic State of Iraq and the Levant (ISIL) had blown themselves up at the army headquarters, which is north of the group's stronghold in Raqa's provincial capital.
Clashes between Syrian army forces and ISIL broke out after the blasts killed several soldiers. The exact number has not been declared yet.
More than 130,000 people are estimated to have been killed since the start of the foreign-hatched conflict against the Syrian government in March 2011.
NTJ/NJF