Syria's military targeted a group of combatants linked to al Qaeda's Nusra Front late on Saturday in southern Syria, state media reported, saying that dozens including three senior members of the group had been killed.
Syria's army and allied combatants from Lebanon's Hezbollah launched a large-scale offensive in the region last month against insurgent groups, including Nusra Front and non-jihadist rebels.
Southern Syria is one of the last areas where mainstream rebels opposing President Bashar al-Assad have a foothold. They have lost ground to hardline Islamist militants in the conflict, which has now entered its fifth year.
"The army... targeted a gathering of terrorists from a group affiliated with Nusra Front in al-Sweiseh in the Quneitra countryside, killing dozens of terrorists including three of their leaders," state news agency SANA said.
A statement from the army mentioned operations in Quneitra province without specifying casualties. The Syrian government describes all insurgents in the civil war as hardline enemies of the state funded by foreign countries.
The Britain-based Syrian Observatory for Human Rights, which tracks the war, said Syrian military helicopters dropped barrel bombs in central Quneitra overnight.
They targeted an area where insurgent Islamic brigades and Nusra Front had been battling Hezbollah and Syrian militias for several weeks, it said.
Rami Abdulrahman, who runs the Syrian Observatory, said it was not clear whether Nusra Front had been hit but that the Syrian air force had carried out more than 150 raids across the country on Friday which had killed dozens of civilians.
Before the southern offensive, Syrian troops had lost control of large areas of countryside near Jordan as well as parts along the frontier with Israel near the Golan Heights, according to regional military analysts and diplomats.