The Islamic State group was "completely besieged" in Al-Bab after forces loyal to Syria's regime cut off a road into the jihadists' last major stronghold in Aleppo province, a monitor said Monday.

"Al-Bab is now completely besieged by the regime from the south, and the Turkish forces and rebels from the east, north and west," said the Syrian Observatory for Human Rights.

It came after "the regime's forces and allied militia seized the only and last main road used by the jihadists between Al-Bab and Raqa," Observatory chief Rami Abdel Rahman told AFP, referring to the jihadists' de facto capital in Syria.