A shroud of black smoke covered the Islamic State group's last redoubt in eastern Syria on Monday as US-backed forces battled holdout jihadists after a night of shelling and heavy air strikes. The SDF has been closing in on IS fighters holed up in a small sliver of territory in the eastern village of Baghouz since January. A cluster of rudimentary tents and vehicles is all that remains of the once-sprawling "caliphate" declared across large swaths of Syria and neighbouring Iraq in 2014.