Syria's army and its allies began an assault on the largest remaining stronghold of Islamic State in Syria and Iraq on Wednesday, Hezbollah-controlled media said, signaling the imminent fall of the militant group's self-proclaimed caliphate.

Islamic State has been all but destroyed over the past two years, remaining only in Albu Kamal in Syria, Rawa in Iraq, in a few neighboring villages and patches of desert, and some isolated pockets elsewhere.

At the height of its power in 2015, it ruled over an expanse of the two countries, eradicating their border, printing money, imposing draconian laws and plotting attacks across the world.