U.S.-backed Iraqi forces fought their way into two villages near Mosul on Monday as the offensive to retake the extremist-held city entered its second week, but they faced questions over a suspected airstrike that hit a mosque, killing 13 people.

Here is a look at the main developments on the eighth day of the Mosul offensive

PUSHING CLOSER TO MOSUL

Iraqi special forces began shelling Islamic State group positions before dawn near Bartella, a historically Christian town to the east of Mosul that they had retaken last week. With patriotic music blaring from loudspeakers on their Humvees, they then pushed into the village of Tob Zawa, about nine kilometers (5 ½ miles) from Mosul, amid heavy clashes.

The Iraqi Federal Police, a military-style force, meanwhile pushed into a small village in the Shura district south of Mosul, where they fired a large anti-aircraft gun and rocket-propelled grenades as they battled IS militants. They later appeared to have secured the village, a cluster of squat homes on a desert plain, and handed out water and other aid to civilians.

The U.S.-led coalition said it had carried out six airstrikes near Mosul on Sunday, destroying 19 fighting positions and 17 vehicles, as well as rocket and mortar launchers, artillery and tunnels.

AIRSTRIKE UNDER INVESTIGATION

Human Rights Watch has called for an investigation into a purported airstrike that struck the women's section of a Shiite mosque in the town of Daquq. The strike happened Friday amid a large Islamic State assault on the nearby city of Kirkuk.

Human Rights Watch said Daquq's residents believe Friday's attack was an airstrike because of the extent of the destruction and because planes could be heard flying overhead.

The U.S. military said it had "definitively determined" that it did not conduct the airstrike that killed civilians in Daquq. The Iraqi military said the government was investigating the attack, and declined to say whether Iraqi or coalition planes were flying in the area at the time of the explosion.

ASSAULT ON DISTANT TOWN

The U.S. military said coalition aircraft were helping Iraqi forces battle IS militants in Rutba a day after they launched a complex attack on the western town, which is hundreds of kilometers (miles) south of Mosul. The Iraqi military said the situation there "is completely under control," and IS militants have no presence inside the town.

The IS-run Aamaq news agency posted a video online that it said showed fighters attacking a military position on Sunday north of Rutba. It said several groups of fighters had infiltrated the town, setting off two car bombs, while other militants attacked the perimeter. Those claims could not be independently confirmed.