More than 220 dead in IS bombings in Syria's Druze heartlands

A series of bomb blasts and shootings carried out by the Islamic State group have killed at least 220 people in southern Syria, the majority civilians, agencies reported on Wednesday.

The death toll from the Suwieda attacks was updated to 221 by the end of Wednesday from an earlier figure of 150, in one of the deadliest attacks by the militants since the war in Syria began in 2011.

"It's the bloodiest death toll in Suweida province since the start of the war," Rami Abdel Rahman, the Syrian Observatory for Human Rights chief told AFP.

"Some residents who fled the attacks on their villages are returning and finding people dead in their homes," Abdel Rahman said. 

IS said "soldiers of the caliphate" carried out the attacks in the Druze heartlands, while the Syrian Observatory for Human Rights reported 127 civilians killed.

The deadly assaults began at around 5:30am when four suicide bombers targeted the provincial capital of Suweida in southern Syria, with two unable to detonate their bomb belts.

A marketplace and residential district were hit by the blasts, with angry residents hanging the bodies of the militants after the attacks.

Other IS militants targeted villages in Suweida with bombings and armed raids, in a province relatively unaffected by the war.

"[Most attacks] were in (Suweida's) northern countryside, where the bodies of civilians executed inside their homes were found," the monitor added.

At least 75 IS militants were killed in the attacks, including the suicide bombers, Reuters reported.

Regime troops and armed villagers managed to fight back and push the IS militants out of the area.

"The city of Suweida is secure and calm now," Governor Amer al-Eshi told state-run Ikhbariyah TV.

IS occupy territories in the Yarmouk Valley basin in southern Syria, where they have remain relatively untouched by a regime ground offensive on surrounding opposition areas.

Regime troops - backed by Russian airstrikes - have managed to capture Daraa province from rebel forces, with the IS enclave likely the next target.

At least 41 civilians have been killed in air raids on the IS territories since 19 July, while 49 regime troops and 67 IS fighters have been killed in clashes, according to the Observatory.

More than 500,000 people have been killed in the war, the vast majority civilians - victims of regime bombing.