Iraqi Prime Minister Haider al-Abadi said the operation to retake the town of Tal Afar, west of Mosul, from the Islamic State group has begun.
Al-Abadi said ISIS fighters inside the town have “no option” but to surrender or die.
Tal Afar and the surrounding area is one of the last pockets of ISIS-held territory in Iraq after victory was declared in July in Mosul, the country’s second-largest city.
The town, about 150 kilometres east of the Syrian border, sits along a major road that was once a key ISIS supply route.
Aid groups have warned the operation could trigger a humanitarian crisis as a stepped up campaign of airstrikes and troop buildup has already forced tens of thousands to flee, according to the United Nations.