KHAZER, Iraq (AP) -- Iraqi and Kurdish forces backed by U.S.-led airstrikes launched coordinated military operations early Monday as the long-awaited fight to wrest the northern city of Mosul from Islamic State fighters got underway. But the battle is likely to be long and it was unclear when the troops would enter the city itself.
The fate of more than a million civilians trapped inside Mosul will also be critical as the battle intensifies in the days and weeks ahead amid concerns that IS could use them as human shields.
Convoys of Iraqi, Kurdish and U.S. forces moved east of Mosul along the front line early Monday as U.S.-led coalition airstrikes sent plumes of smoke into the air and heavy artillery rounds rumbled in the distance.
Iraqi Prime Minister Haider al-Abadi announced the start of the operations on state television, launching the country's toughest battle since American troops left nearly five years ago.
Mosul, Iraq's second largest city, fell to IS in the summer of 2014, and weeks later the head of the extremist group, Abu Bakr al-Baghdadi, announced the formation of a self-styled caliphate from the pulpit of one of its mosques.
"These forces that are liberating you today, they have one goal in Mosul which is to get rid of Daesh and to secure your dignity," al-Abadi said, addressing the city's residents and using the Arabic acronym for IS. "God willing, we shall win."
If successful, the liberation of Mosul would be the biggest blow yet to the Islamic State group. Al-Abadi pledged the fight for the city would lead to the liberation of all Iraqi territory from the militants this year.
In Washington, Defense Secretary Ash Carter called the launch of the Mosul operation "a decisive moment in the campaign" to deliver a lasting defeat to IS.
Iraqi forces have been massing around Mosul in recent days, including elite special forces that are expected to lead the charge into the city, as well as Kurdish forces, Sunni tribal fighters, federal police and state-sanctioned Shiite militias.
South of Mosul, Iraqi military units are based at the sprawling Qayara air base, but to the city's east, men are camped out in abandoned homes.
Kurdish forces are stationed to the north and east of Mosul, a mostly Sunni city that has been a center of insurgent activity and anti-government sentiment since the U.S.-led invasion of Iraq in 2003. Iraqi officials have warned that the Mosul operation has been rushed before a political agreement has been set for how the city will be governed after IS.
Lt. Col. Amozhgar Taher with Iraq's Kurdish forces, also known as the peshmerga, said his men would only move to retake a cluster of mostly Christian and Shabak villages east of Mosul and would not enter the city itself due to their concern for "sectarian sensitivities." Taher spoke at a makeshift base in an abandoned house along the front line, some 30 kilometers (19 miles) east of Mosul.
Later Monday, Turkey's state-run Anadolu news agency said the peshmerga have taken control of seven villages east of Mosul and that they control the main road linking the city with the Iraqi Kurdish regional capital, Irbil, further to the east.
Iraqi special forces Lt. Col. Ali Hussein said the Kurdish forces are leading the first push on Mosul's eastern front. His men were anxious to move out to the front line, though he said he expects they will wait near the town of Khazer for another day or two.
Meanwhile, a suicide car bombing targeted security forces outside Baghdad, killing at least 12 people and wounding more than 30 on Monday, officials said, speaking on condition of anonymity as they were not authorized to talk to the media. Nobody immediately claimed responsibility for the checkpoint attack in the town of Youssifiyah, 20 kilometers (12 miles) south of Baghdad, though it bore the hallmarks of the Islamic State group.
Mosul fell to IS during the militants' June 2014 blitz that left nearly a third of Iraq in the extremists' hands and plunged the country into its most severe crisis since the U.S.-led invasion. It became part of the IS group's self-styled caliphate, which at that time stretched across a third of both Syria and Iraq.
But over the past year, the militants have suffered a series of major defeats in both Syria and Iraq, where their area of control is now limited to Mosul and some smaller towns. Mosul is about 360 kilometers (225 miles) northwest of the capital, Baghdad.
The operation to retake Mosul is expected to be the most complex yet for Iraq's military, which has been rebuilding from its humiliating 2014 defeat.
U.S. Lt. Gen. Stephen Townsend, commander of the anti-IS coalition, said in a statement that the operation to regain control of Mosul could take "weeks, possibly longer."
Earlier, Iraqi Brig. Gen Haider Fadhil told The Associated Press that more than 25,000 troops, including paramilitary forces made up of Sunni tribal fighters and Shiite militiamen, will take part in the offensive that will be launched from five directions around the city.
The role of the Shiite militias has been particularly sensitive, as Nineveh, where Mosul is located, is a majority Sunni province. Shiite militia forces have been accused of carrying out abuses against civilians in other Sunni areas.
Fadhil voiced concern about potential action from Turkish troops based in the region of Bashiqa, northeast of Mosul. Turkey sent troops to the area late last year to train anti-IS fighters. But Baghdad views the Turkish presence as a "blatant violation" of Iraqi sovereignty and has demanded the Turkish troops withdraw.
Turkey's deputy prime minister said some 3,000 Turkish-trained Iraqi fighters are taking part in the operation to wrest Mosul from IS. Numan Kurtulmus also told reporters Monday that Turkey has no intention of withdrawing its troops, who he said had trained 4,000 local fighters, three fourths of which had joined the battle alongside the peshmerga.
Military operations are predicted to displace 200,000 to a million people, according to the United Nations. Just a few kilometers from the eastern front line, rows of empty camps for displaced civilians line the road, but aid groups say they only have enough space for some 100,000 people.
In Geneva, a senior U.N. official said he's "extremely concerned" for the safety of civilians in Mosul. Stephen O'Brien, the undersecretary-general for humanitarian affairs and emergency relief coordinator, said that as many as "1 million people may be forced to flee their homes in a worst-case scenario."
He warned that families are at "extreme risk" of being caught in crossfire, and that tens of thousands may end up besieged or held as human shields, and thousands could be forcibly expelled.
In the midst of a deep financial crisis, the Iraqi government says it lacks the funds to adequately prepare for the humanitarian fallout of the Mosul fight. In some cases commanders say they are encouraging civilians to stay in their homes rather than flee.
"While we may be celebrating a military victory" after Mosul is liberated, said Falah Mustafa, the foreign minister for Iraq's Kurdish region, "we don't want to have also created a humanitarian catastrophe."