The state SANA news agency says the Wednesday morning attack happened in the province of Sweida.
The Britain-based Syrian Observatory for Human Rights says a series of what appeared to be suicide blasts in the southern province killed 32 people, including the attackers. The different tolls could not immediately be reconciled.
The rare attacks in Sweida coincide with a government offensive in southern Syria, where troops are fighting an IS-affiliated group near the frontier with the Israeli-occupied Golan Heights area and other areas in the south.
Government forces have previously retaken territories controlled by the rebels in the border area and are now fighting militants there.