Islamic State has claimed responsibility for a series of deadly attacks and suicide blasts in southern Syrian city of Sweida that killed dozens of people.

The militant group said its “soldiers” carried out surprise attacks on government and security centres in the city on Wednesday.

The blast site
Syrians inspect the site of a suicide attack in Sweida (SANA/AP)

The bombings – including a suicide attack at a busy vegetable market and a city square – sparked clashes later in the day between Syrian troops and allied militias and IS militants.

IS said more than 100 people were killed.

A Syrian local health official said the bombings and co-ordinated attacks, as well subsequent fighting between local armed groups and militants in Sweida, killed more than 90 in all.

A poster of Bashar Assad
The attacks are the worst in months (AP)

The attacks – the worst in recent months – had all the hallmarks of IS even before it claimed responsibility and were reminiscent of the group’s assaults over the past few years in Syria.

The bombings in the city of Sweida, including a motorcycle bomber who struck at a busy vegetable market, were apparently timed to coincide with attacks by a militant group linked to IS on a number of villages in the province, also called Sweida.

It triggered deadly clashes between pro-government fighters and residents who picked up weapons to defend their hometowns on one side, and IS militants on the other.

Al-Ikhbariya state-run TV showed images from several locations in the province and its capital where the bombers blew themselves up.

Syrian troops
Syrian troops flash the victory sign next to the Syrian flag in Tell al-Haara (AP)

The rare attacks in Sweida, populated mainly by Syria’s minority Druze, came amid a government offensive elsewhere in the country’s south.

Government forces are battling an IS-linked group near the frontier with Israeli-occupied Golan Heights and near the border with Jordan. The group also has a small presence on the eastern edge of Sweida province.

IS has been largely defeated in Syria and Iraq, but still has pockets of territory it controls in eastern Syria and in the country’s south.

Since their offensive in June, Syrian President Bashar Assad’s forces have retaken territories controlled by the rebels along the Golan Heights frontier and are now fighting militants in the country’s southern tip.