Iraqi forces advanced into a town south of Mosul Saturday as an Iraqi Shi'ite militia joined the offensive by opening up a new front to the west.
Iraqi troops approaching Mosul from the south advanced into Shura after a wave of U.S.-led airstrikes and artillery shelling against militant positions inside the town.
Commanders said most Islamic State (IS) fighters withdrew earlier this week, using civilians as human shields, but that U.S. airstrikes had disrupted the forced march, helping some civilians to escape.
Iraqi soldiers and Kurdish forces, known as peshmerga, are advancing on Mosul from the south, east and north, capturing villages and disarming Islamic State booby traps.
To the west of the city, Iraq's state-sanctioned Shi'ite militias, backed by Iran, have launched an assault aimed at driving IS from the town of Tal Afar to try to secure the western border with Syria.
That could cut-off critical weapons and supply routes between Mosul and the Syrian city of Raqqa, an IS stronghold.
There are concerns the militias could inflame sectarian tensions in the Sunni-majority city, but commanders have said they will not enter the city itself.
According to U.N.-cited reports IS has forcibly taken civilians into Mosul. The reports say that in just two days earlier this week, IS-fighters killed more than 250 people who resisted or who were previously members of Iraqi security forces.
More than 17,500 people have fled their homes toward government-held areas since the Mosul operation began, the International Organization for Migration said Saturday. That number is expected to sharply rise as the battle continues.
Iraqi forces launched a massive offensive to retake militant-held Mosul last week, Iraq's second-largest city, home to more than 1 million people. The battle for Mosul is expected to take weeks, if not months.