Iraq pushes into town near Mosul

Iraqi troops are mounting a major attack to recapture a mostly Christian town near the key city of Mosul from the Islamic State.

Islamic State militants have launched a major attack on the Iraqi city of Kirkuk. (AAP)

Iraqi forces have pushed into a town near the Islamic State-held city of Mosul after a wave of militant attacks in and around the northern city of Kirkuk set off more than 24 hours of heavy clashes, with ongoing skirmishes in some areas.

US Defense Secretary Ash Carter meanwhile arrived in Baghdad on an unannounced visit to meet with Iraqi commanders to discuss the offensive to retake Mosul, which the US is supporting with airstrikes and advisers on the ground.

The Iraqi army said the 9th Division has pushed into the town of Hamdaniyah, also known as Qaraqosh and Bakhdida, and raised the flag over its central government compound, but the troops were likely still facing resistance in and around the town. Similar past announcements have often proved premature.

The town is around 20km from Mosul. Iraqi forces launched a wide-scale offensive earlier this week aimed at retaking Mosul, the country's second largest city, which fell to IS in 2014.

Hamdaniyah is believed to be largely uninhabited. IS has heavily mined the approaches to Mosul, and Iraqi forces have had to contend with roadside bombs, snipers and suicide truck bombs as they move closer to the city.

Iraqi forces retook the town of Bartella, around 15km east of Mosul, earlier this week, but are still facing pockets of resistance in the area.

Inside Bartella, a road extending more than 100 metres was completely demolished, with all the homes on either side reduced to rubble. IS graffiti was scrawled across the walls, and the militants appeared to have renamed streets and neighbourhoods after famous fighters during the more than two years they controlled the area.

In Kirkuk, meanwhile, some fighting continued a day after IS launched a massive attack in and around the city, some 170km southeast of Mosul. The assault appeared to be an attempt to divert attention from Mosul.

The area around the provincial headquarters, where the fighting was heaviest on Friday, was quiet. But witnesses said there were ongoing clashes in the Asra wa Mafkudin neighbourhood, where at least two IS fighters were killed on Saturday. They spoke on condition of anonymity out of security concerns.