SHURA, Iraq -- State-sanctioned Shiite militias joined Iraq's Mosul offensive Saturday with a pre-dawn assault to the west, where they hope to complete the encirclement of the Islamic State-held city and sever supply lines from neighboring Syria.
Other Iraqi forces aided by U.S.-led airstrikes and heavy artillery meanwhile drove the Islamic State from the town of Shura, south of Mosul, where the militants had rounded up civilians to be used as human shields.
The twin thrusts come nearly two weeks into the offensive to retake Iraq's second-largest city, but most of the fighting is still taking place in towns and villages far from its outskirts, and the entire operation is expected to take weeks, if not months.
The involvement of the Iran-backed Shiite militias has raised concerns that the battle for Mosul, a Sunni-majority city, could aggravate sectarian tensions. Rights groups have accused the militias of abuses against civilians in other Sunni areas retaken from the Islamic State, accusations the militia leaders deny.
The umbrella group for the militias, known as the Popular Mobilization Units, said they will not enter Mosul itself and will instead focus on retaking Tal Afar, a town to the west that had a Shiite majority before it fell to the Islamic State in 2014.
Ahmed al-Assadi, a spokesman for the group, told reporters in Baghdad that the militias had retaken 10 villages since the start of the operation. But there was likely still some fighting underway, and he said forces were removing explosive booby traps left by the Islamic State to slow their advance.
Jaafar al-Husseini, a spokesman for the Hezbollah Brigades, said his group and the other militias had advanced 4 miles toward Tal Afar and used anti-tank missiles to destroy three suicide car bombs that were heading toward them.
He said the U.S.-led coalition, which is providing airstrikes and ground support to the Iraqi military and Kurdish forces known as the peshmerga, is not playing any role in the Shiite militias' advance. He said Iranian advisers and Iraqi aircraft were helping them.
The presence of Iranian-backed militias could give Turkey, which has insisted on a role in the Mosul operation despite opposition from Baghdad, an excuse to deepen its involvement.
Turkey has said it has a duty to protect the people of Tal Afar, who are ethnic Turkmen, but it also has a strategic interest in countering Iranian influence in Iraq. It has stationed hundreds of troops near Mosul and trained Sunni fighters, ignoring Baghdad's repeated requests for the Turks to leave.
Any Turkish forces in Iraq will be dealt with "as the enemy," said Jawad al-Tleibawi, a spokesman for the Asaib Ahl al-Haq Shiite militia. "We already have plans to confront any intervention by them," he said. Tleibawi said Shiite militias also planned to retake Hatra and Baaj, putting them in the vicinity of Kurdish peshmerga forces, who have clashed with them in the past.
U.S. diplomats earlier this month failed to broker an agreement between Turkey and Iraq about what role the Turks would play in the offensive.
Many of the militias were originally formed after the 2003 U.S.-led invasion to battle American forces and Sunni insurgents. They were mobilized again and endorsed by the state when the Islamic State swept through northern and central Iraq in 2014.
Iraqi troops approaching Mosul from the south advanced into Shura after a wave of U.S.-led airstrikes and artillery shelling against militant positions inside the town. Commanders said most of the Islamic State fighters withdrew last week with civilians, but that U.S. airstrikes had disrupted the forced march, allowing some civilians to escape.
"After all this shelling, I don't think we will face much resistance," Iraqi army Maj. Gen. Najim al-Jabouri said as the advance got underway. "This is easy, because there are no civilians left," he added.
But hours later, a few families who had hunkered down during the fighting emerged. The government has urged people to remain in their homes, fearing a mass exodus from the Mosul area, which is still home to more than 1 million people.
By the afternoon, Brig. Gen. Firas Bashar said his forces were clearing explosives and searching for Islamic State fighters in Shura. The sound of artillery echoed in the distance.
In Baghdad, meanwhile, an Islamic State suicide bomber targeting an aid station for Shiite pilgrims killed at least seven people and wounded more than 20, police and hospital officials said, speaking on condition of anonymity as they were not authorized to brief reporters.
The Sunni extremist group often targets Iraq's Shiite majority, which it views as apostates deserving of death.
The Mosul offensive involves more than 25,000 soldiers, federal police, Kurdish fighters, Sunni tribesmen and the Shiite militias.
Iraqi forces moving toward the city from several directions have made uneven progress since the offensive began Oct. 17. They are 4 miles from the edge of Mosul on the eastern front, where Iraq's special forces are leading the charge. But progress has been slower in the south, with Iraqi forces still 20 miles from the city.
The U.N. human-rights office said Friday that the Islamic State has rounded up tens of thousands of civilians in and around Mosul to use as human shields, and has massacred more than 200 Iraqis in recent days, mainly former members of the security forces.
The militants have carried out mass killings of perceived opponents in the past and boasted about them in grisly photos and videos circulated online. The group is now believed to be cracking down on anyone who could rise up against it, focusing on men with military training or past links to the security forces.
Elsewhere, pathologists at the Kirkuk hospital morgue were undertaking the gruesome process of gathering intelligence on the Islamic State's sudden counterattack on the city by analyzing the corpses of 84 militants.
One by one, the bodies were removed from black body bags so fingerprints and DNA could be preserved. If no relatives claim the remains, the bodies will be burned.
A counterterrorism unit, meanwhile, was searching the fighters' cellphones for data and trying to find any residents who might have been on the calls. They were trying to discern whether the city is still at risk of infiltration or another assault.
"What they did to us inside Kirkuk was by far the worst we have ever seen," said Polad Talabani, the commander of the Kurdish counterterrorism force, which was summoned from nearby Sulaimaniya to help put down the assault that drove deep into the city's heart before dawn Oct. 21.
Beyond the militants, 116 people were killed in the fighting, including 43 police officers, 33 peshmerga and other security force personnel, and 21 civilians, among them several Iranian technicians who worked at a power plant, officials said. About 265 people were wounded.
Information for this article was contributed by Susannah George, Qassim Abdul-Zahra, Joseph Krauss and Maamoun Youssef of The Associated Press; by Loveday Morris and Mustafa Salim of The Washington Post; and by Michael R. Gordon and Kamil Kakol of The New York Times.
A Section on 10/30/2016