A rebel alliance, including Al-Qaeda's Syria affiliate Al-Nusra Front, attacked government-held parts of the southern city of Daraa on Thursday, a monitoring group said.
The alliance, also involving powerful Islamist group Ahrar al-Sham, bombarded loyalist positions with mortar and artillery fire, the Syrian Observatory for Human Rights said.
Syria's official SANA news agency said "terrorists hit neighbourhoods of Daraa city with mortar rounds and gas canister bombs," adding that there were reports of casualties.
"Army units foiled attempts by terrorist groups to attack several military positions in Daraa province destroying several armoured vehicles and killing dozens of terrorists," state television said.
It made no mention of fighting inside Daraa city, parts of which are already under rebel control.
Around 70 percent of Daraa province is under the control of rebel groups, who have made several advances in the region in recent weeks.
In early June, rebels from the Southern Front coalition seized the 52nd Brigade base and advanced to the border between Daraa and Sweida, a mainly Druze province to the east which is largely regime-controlled.