State-sanctioned Shi'ite militias have joined Iraq's Mosul offensive with a pre-dawn assault to the west, where they hope to complete the encirclement of the Islamic State-held city and cut supply lines from neighbouring Syria.
Other Iraqi forces aided by US-led air strikes and heavy artillery meanwhile drove Islamic State militants from the town of Shura, south of Mosul, where the militants had rounded up civilians to be used as human shields.
Saturday's 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 Iranian-backed Shi'ite 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 IS, accusations the militia leaders deny.
The umbrella group for the militias, known as the Popular Mobilisation Units, says they will not enter Mosul itself and will instead focus on retaking Tal Afar, a town to the west that had a Shi'ite majority before it fell to IS 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 pre-dawn operation. But there was likely still some fighting underway, and he said forces were removing explosive booby-traps left by IS to slow their advance.
Jaafar al-Husseini, a spokesman for the Hezbollah Brigades, said his group and the other militias had advanced 7km toward Tal Afar and used anti-tank missiles to destroy three suicide car bombs that were heading toward them.
He said the US-led coalition, which is providing air strikes and ground support to the Iraqi military and Kurdish forces known as the peshmerga, is not playing any role in the Shi'ite militias' advance. He said Iranian advisers and Iraqi aircraft were helping them.
Many of the militias were originally formed after the 2003 US-led invasion to battle American forces and Sunni insurgents. They were mobilised again and endorsed by the state when IS swept through northern and central Iraq in 2014.
Iraqi troops approaching Mosul from the south advanced into Shura after a wave of US-led air strikes and artillery shelling against militant positions inside the town. Commanders said most of the IS fighters withdrew earlier this week with civilians, but that US 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 Major General 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 Mosul, which is still home to more than 1 million people.
The Mosul offensive involves more than 25,000 soldiers, Federal Police, Kurdish fighters, Sunni tribesmen and the Shiite militias.
The UN human rights office said on Friday that IS 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.
