AKIPRESS.COM - Kurdish fighters say they have launched a large-scale operation east and north of Mosul, as an offensive to oust so-called Islamic State (IS) militants from the Iraqi city continues, BBC reports.

The Kurds say the operation aims to tighten the noose around the militants' last major stronghold in Iraq.

The Iraqi army has been moving from the south, and special forces have now joined the offensive.

There are signs that IS leaders have fled Mosul, the US military says.

There are thought to be up to 5,000 IS fighters still in the city.

The Kurdish fighters said their operation was on three fronts, and followed recent gains by both the Kurds and the Iraqi security forces in the area.

"The objectives are to clear a number of nearby villages and secure control of strategic areas to further restrict Isil's [IS] movements," the statement said.

Mosul has been in the hands of IS since 2014 and is the militants' last major Iraqi stronghold.

The offensive to retake it began on Monday, with the advancing forces seizing a number of villages on the city's outskirts ahead of a final push into the city.

But progress is expected to be slow, with IS fighters appearing to be putting up stiff resistance in places.

There are warnings the group could use human shields or chemical weapons.