A string of suicide blasts and raids claimed by the Islamic State group killed more than 220 people in southern Syria on Wednesday, in one of the jihadists’ deadliest ever assaults in the country.

The Syrian Observatory for Human Rights said the attacks hit several areas of the largely government-held southern province of Sweida, where IS retains a presence in a northeastern desert region.

The bloodshed came almost a week into a Russia-backed regime campaign to oust IS fighters from a holdout in a neighbouring province of the country’s south.