Security officials said on Wednesday that Iraqi-led forces had succeeded in cutting off Mosul from its western supply lines, with the "Islamic State" (IS) now effectively under siege in and around the city.

The news was confirmed by peshmerga sources, who said that the largely Shiite and Arab Popular Mobilization militia had gained control of the road leading southwest from Tal Afar to the Syrian border.

Tal Afar, which lies some 60 kilometers (35 miles) to the east of the much larger city of Mosul, is on the last remaining route to Syria.  The militia advance means IS forces are hemmed in between Mosul's eastern outskirts, where Iraqi troops are fighting their way into the city, and the Tel Afar area.

Iraqi forces, backed by a US-led air alliance, began their offensive to take back Mosul, Iraq's second-largest city in mid-October.

In eastern Mosul, Iraqi special forces are slowly fighting their way towards the city center, but are faced with suicide car bombings, booby traps and snipers. Meanwhile, they are hampered by the problem of having to fight an enemy that has no qualms about using human shields.

Meanwhile, the Popular Mobilization units have surrounded the town of Tal Afar - which had a Shiite majority before it fell to IS.

The UN says at least 68,000 people have fled the fighting in Mosul, including some 8,300 over the past four days. The Associated Press reported that many of those fleeing were viewed with initial suspicion as they approached Iraqi troops, who feared they may be hiding car bombs.

Mosul fell to IS in the summer of 2014, and is still home to more than a million people. Authorities, worried about the difficulties that would be posed by a mass exodus, have told residents to remain inside their homes.

rc/bw (AP, AFP, dpa, Reuters)