As many as 4,500 ISIS fighters are entrenched in the city and are expected to fight tooth and nail.
With the support of Iran and a US-led coalition, Iraqi forces have since regained much of the ground lost to IS and Mosul is the extremist group's last major stronghold in Iraq. "Do you want to be treated badly by the army as they used to treat you before we liberated you?" A phone number for Mosul residents to report ISIS activity is included.
A victory in Mosul would be a huge blow to the Islamic State, pushing it out of the last major urban center under its control in Iraq.
If the civilians stay in the city, they become victims of airstrikes, street battles and a seige by the forces. What is unknown is how stiff a defense ISIS fighters will put up to defend the city.
"The force leading liberation operations is the courageous Iraqi army with the national police and they are the ones that will enter Mosul, not others", Abadi said, in reference to Iranian-backed Shi'ite militias that will not be involved in the operation.
Convoys of Iraqi, Kurdish and US forces could be seen moving east of Mosul into the early hours of the day.
ISIS also is releasing some low-level prisoners, the source said, such as those jailed for their beards, cigarettes or clothing offenses. Wounded ISIS fighters have been told to go to Raqqa, Syria, the group's de facto capital, the source said.
In his keynote speech to mark the beginning of the academic year at the Recep Tayyip Erdogan University in northern Turkey's Rize province, Erdogan referred to the upcoming military campaign to retake the ISIL-held city of Mosul.
Among the groups joining to fight ISIS in Mosul are the Shia-led Hashd Al-Shaabi, or Popular Mobilization Unit. "We are your ally", Erdogan said. He said the PMU forces also include Christians, Yazidis and Turkmen.
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Given that California is the nation's top issuer of municipal debt, their sanctions could cost the bank millions. Kasich said he may re-access the decision if the company makes progress in restoring a "culture of integrity".
A Mosul resident said by phone, "All the people I talk to are ready to rebel against [Islamic State] with the first gunshot of the operation". But even now, as Iraqi forces appear to be firing the opening salvo in the most important battle so far against ISIS, U.S. officials have said how Mosul falls will be as important to its future-and the ability of groups like ISIS to return there-as the timing of its fall.
US military officials estimate there are 3,500 to 5,000 ISIS fighters in Mosul.
Kurdistan Regional Government President Massoud Barzani announced Sunday the start of the offensive in a statement posted online, saying "the preparation for the operation to liberate Mosul have been completed and have paved the way to begin the Mosul operation".
Later Saturday, 14 members of ISIS were executed after trying to flee with their families from Mosul to Raqqa, the witnesses said. Abadi has pledged to have the city back under Iraqi government control by the end of the year.
NRC reiterates its appeal to the parties to the conflict to guarantee the safety of women, children and men who have lived for more than two years under brutal oppression, by establishing safe exit routes as the topmost priority.
The militants have dug a 7ft-by-7ft trench on the perimeter of the city, which they plan to fill with burning oil when the troops move in to obscure their view.
The UN has warned that the fighting could have an "enormous" humanitarian impact on the city.
Baghdad still suffers frequent explosions, auto bombs and suicide attacks, mainly in crowded areas.
ISIS also released some low-level prisoners, including those jailed for their beards, cigarettes or clothing, the source added.