Syrian government forces have advanced towards Islamic State terror group's last major stronghold in Aleppo province, cutting off the main supply route into al-Bab.<br/><br/>The Syrian Observatory for Human Rights said troops have captured Tal Uwayshiya, a hill 9 kilometers to the south-east. It overlooks a key road linking al-Bab to the IS-controlled city of Raqqa, in a neighbouring province. Al-Bab is now almost surrounded by Turkish-backed Syrian rebels. The rebels are laying siege from the north, east and west.