Mosul Iraq battle: Shia militias aim to take Tal Afar
The Hashid Shaabi groups say their aim is to oust IS from the town of Tal Afar, cutting jihadist supply routes to Mosul from Syria.
Tal Afar had a Shia majority before IS overran it in 2014. Mosul is a Sunni city, and the Shia militias have pledged not to enter it.
Iraq began the offensive last week.
Iraqi, Kurdish and allied forces, backed by US air power, have advanced in their push to retake Mosul, IS's de facto capital in Iraq.
"The operation aims to cut supplies between Mosul and Raqqa (IS's de facto capital in Syria) and tighten the siege... in Mosul and liberate Tal Afar," Hashid Shaabi spokesman Ahmed al-Assadi told the AFP news agency.
He added that the operation was launched from an area south of Mosul.
During previous military campaigns against IS, Shia militia groups have been accused of committing serious crimes, including war crimes, against Sunni civilians.
As many as 1.5 million people are believed to remain in Mosul.
There are fears IS could use them as human shields as the operation closes in on the city.
On Friday, the UN said that IS militants had abducted tens of thousands of civilians from areas around the city to use them as human shields.
The jihadist group has also killed some 190 former members of Iraq's security services and 42 civilians, apparently for refusing to obey its orders, the UN added.
Source: bbc.com