Iraq's Shiite militias say they will participate in the next major battle against the Islamic State group after the Iraqi forces' victory in Mosul last month.

The Shite militias did not fight in the urban part of Mosul, Iraq's second-largest city, but were key in clearing far-flung villages of IS and capturing supply lines in the desert west of Mosul toward Iraq's border with Syria.

The spokesman for the government-sanctioned umbrella — known as the Popular Mobilization Forces, and mostly made up of Shiite militias — says the participation of the militiamen is "essential" in the upcoming fight for the town of Tal Afar, west of Mosul.

Ahmed al-Asadi spoke to reporters in Baghdad on Monday.

The militias have been accused of sectarian killings and other abuses against Sunni civilians.