Militants killed dozens of people in a series of attacks in southern Syria on Wednesday, including suicide bombings in the city of Sweida.

Northeast of the city, Islamic State militants clashed with government forces as they launched simultaneous attacks on several villages, according to state media and a war monitoring group.

At least two attackers blew themselves up in Sweida, near a marketplace and in another district, state television said.

Sweida Governor Amer al-Eshi said authorities killed two militants before they could detonate explosive belts and arrested a third attacker. "The city of Sweida is secure and calm now," he told state-run Ikhbariyah TV.

The multiple attacks killed at least 38 civilians and wounded 37 others in the city and its countryside, the head of the Sweida health authority told state TV.

The Syrian Observatory for Human Rights, a UK-based monitoring group, said government forces battled jihadists who stormed the villages from an Islamic State pocket northeast of the city.

Syrian government troops and their allies hold all of Sweida province except for that enclave.

The air force pounded militant hideouts northeast of the city after soldiers thwarted an attempt by Islamic State fighters to infiltrate Douma, Tima and al-Matouna villages, state media said.

The army and local villagers regained control of a hill and broke a brief siege of another nearby village after clashes, Ikhbariyah said.

With the help of Russian air power, the Syrian army has been hitting Islamic State in a separate pocket further west, near the frontier with the Israeli-occupied Golan Heights.

The Yarmouk Basin in southwest Syria remains in jihadist hands, after an army offensive defeated rebel factions in other parts of the southwest. The operation has focused on Deraa and Quneitra provinces.