KHAZER, Iraq (AP) — Iraqi and Kurdish forces advanced on a town near Mosul on Sunday as part of an operation to retake the northern city from the Islamic State group, which staged an assault in western Iraq that appeared to be another diversionary attack.

The Kurdish forces, known as peshmerga, said they "cordoned off" eight villages northeast of Mosul and are now less than 9 kilometers (5 ½ miles) from its outskirts. They said the cordoned off area measures around 100 square kilometers (38 square miles), and that they also secured a "significant stretch" of highway.

The statement said eight car bombs were destroyed in the operation, including three by U.S.-led coalition aircraft, and "dozens" of militants were killed.

Those gains came after Iraqi and Kurdish forces launched an offensive against the nearby town of Bashiqa. Maj. Gen. Haider Fadhil, of Iraq's special forces, said they had also taken part in the operation, and that the town was surrounded.

Over the last week, Iraqi and Kurdish forces have been battling IS in a belt of mostly uninhabited towns and villages around Mosul, contending with roadside bombs, snipers and suicide truck bombs.

In western Iraq, IS militants stormed into the town of Rutba, unleashing three suicide car bombs that were blown up before hitting their targets, according to the spokesman for the Joint Military Command, Brig. Gen. Yahya Rasool.

He said some militants were killed, without giving an exact figure, and declined to say whether any civilians or Iraqi forces were killed. He said the militants did not seize any government buildings and that the situation "is under control."

The IS-run Aamaq news agency had earlier said militants stormed Rutba from several directions.

Lt. Gen. Stephen Townsend, the top U.S. commander in Iraq, confirmed there had been a complex attack in Rutba and said he expects more such attacks as the militants try to divert attention from Mosul.

IS carried out a large assault on the northern city of Kirkuk on Friday, in which more than 50 militants stormed government compounds and other targets, setting off more than 24 hours of heavy fighting and killing at least 80 people, mainly security forces.

The Mosul offensive involves more than 25,000 Iraqi ground forces as well as U.S.-led coalition aircraft and advisers. It is expected to take weeks, if not months, to drive IS from Mosul, which is home to more than a million civilians.

Bashiqa is close to a military base of the same name where some 500 Turkish troops are training Sunni and Kurdish fighters for the Mosul offensive.

The presence of the Turkish troops has angered Iraq, which says it never gave them permission to enter the country and has called on them to withdraw. Turkey has refused, insisting that it play a role in retaking Mosul from IS.

U.S. Defense Secretary Ash Carter has visited both countries in recent days, and arrived in the Kurdish regional capital, Irbil on Sunday.

After meeting with Turkey's leaders, Carter had announced an "agreement in principle" for Turkey to have a role in the operation. But Iraqi Prime Minister Haider al-Abadi told Carter on Saturday that Mosul was an "Iraqi battle."

The forces taking part in the Mosul offensive include Iraqi troops, the peshmerga, Sunni tribal fighters and state-sanctioned Shiite militias. Many fear the operation could heighten tensions between Iraq's different communities, which are allied against IS but divided over a host of other issues, including the fate of territories near mostly Sunni Mosul that are claimed by the largely autonomous Kurdish region and the central government.

Carter praised the peshmerga, saying they "fight extremely well," but also acknowledged that they had suffered casualties.

Brig. Gen. Halgord Hekmet, a spokesman for the Kurdish forces, told reporters that 25 of their troops have been killed since the battle to retake Mosul began and a "large number" had been wounded.

He said the peshmerga have had good coalition air support, but could use more armored vehicles and roadside bomb detectors. Most of the fallen peshmerga were riding in regular cars, he said.

The U.N. agency for children meanwhile expressed concern over the more than 4,000 people it says have fled from areas around Mosul since the operation began.

UNICEF's Iraq representative, Peter Hawkins, said that in at least one refugee camp the conditions for children were "very, very poor." He said UNICEF teams delivered water, sanitation and other supplies expected to last seven days.

They also provided immunizations against polio and measles, which he said had not been available during the more than two years that the people lived under IS rule. UNICEF has plans to assist more than 784,000 people, including up to 500,000 children.

Hawkins says children in and around Mosul are at risk of death or injury from the fighting, as well as sexual violence, kidnapping and recruitment by armed groups.

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Krauss reported from Baghdad. Associated Press writers Sinan Salaheddin in Baghdad, Lolita C. Baldor in Irbil, Iraq, and Maamoun Youssef in Cairo contributed to this report.