Islamic State has bolstered its forces north of Syria’s second city Aleppo, where it is attacking rivals as part of a broader push beyond its eastern strongholds, a rebel leader and a monitoring group said.

The radical jihadist group has in recent weeks conducted a series of attacks in western areas of Syria including state-held territory and has also staged a major advance into Damascus, where it is battling for control of the Yarmouk refugee camp.

Earlier this week, the group targeted rival rebel factions north of Aleppo with two car bombs, killing at least 31 people, according to the Syrian Observatory for Human Rights, which monitors the conflict. […]