Elite Iraqi forces on Thursday retook a town on the eastern edge of Mosul while Kurdish peshmerga opened a new front in the offensive to wrest back the jihadists' last bastion in Iraq.
Prime Minister Haider al-Abadi told an international meeting in Paris that the four-day-old offensive was "advancing faster than expected".
France and Iraq were co-chairing the meeting on the future of Mosul, which observers have warned could raise even greater humanitarian and interconfessional challenges than the massive military operation to retake it.
In some areas, the Iraqi advance was met by a trickle of civilians fleeing both the fighting and the jihadists who ruled them for two years, but the feared mass exodus from Mosul had yet to materialise.
The counter-terrorism service (CTS), Iraq's best-trained and most battle-seasoned force, retook full control of Bartalla, a town that lies less than 15 kilometres east of Mosul.
"I announce to the people of Bartalla and Mosul we have complete control over Bartalla," CTS commander Taleb Sheghati al-Kenani told reporters from the town.
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"Its residents, its churches and all of its infrastructure are now under the control of CTS," he said of the small Christian town that IS seized when it swept across the Nineveh plain in August 2014.
Some 120,000 Iraqi Christians were forced to flee their homes at the time.
Further north Kurdish peshmerga forces opened a new front with a multiple-pronged assault on the town of Bashiqa.
"The objectives are to clear a number of nearby villages and secure control of strategic areas to further restrict ISIL's movements," the peshmerga command said, using an alternative acronym for IS.
At dawn, bulldozers flattened a path for forces in armoured vehicles to carve their way down towards Bashiqa.
As tanks and personnel carriers prepared to advance, a shadow glided above them and one peshmerga shouted "drone!"
Fighters opened fire at it with every weapon available, causing an almighty din and lighting up the dim morning sky, until it fell to the ground and the troops resumed their advance.
An AFP reporter in the village of Nawaran near Bashiqa saw the downed drone, a Raven RQ-11B model similar to a booby-trapped one that killed two Kurdish fighters and wounded two French soldiers a week ago.
Iraqi federal forces and the peshmerga have not divulged casualty figures in this offensive.
On Thursday, IS released a short video showing the bodies of what it said were two peshmerga, hung by their feet from a bridge in central Mosul.
A US service member was killed today when an improvised explosive device went off, the coalition said.