Turkey, which has a base in the area, said Sunday it had provided artillery support following a request from the peshmerga
Iraqi forces advancing on Mosul faced stiff resistance from the Islamic State group on Monday despite the US-led coalition unleashing an unprecedented wave of air strikes to support the week-old offensive.
Federal forces and Kurdish peshmerga fighters were moving forward in several areas, AFP correspondents on various fronts said, but the jihadists were hitting back with shelling, sniper fire, suicide car bombs and booby traps.
IS has also attempted to draw attention away from losses around Mosul with attacks on Iraqi forces elsewhere in the country, the latest coming on Sunday near the Jordanian border.
Following a weekend visit to Iraq by US Secretary of Defence Ashton Carter, American officials said the coalition was providing the most air support yet to the operation.
"One week into Mosul operation, all objectives met thus far, and more coalition air strikes than any other 7-day period of war against ISIL (IS)," Brett McGurk, the top US envoy to the 60-nation coalition, wrote on social media.
"There were 32 strikes with 1,776 munitions delivered against Daesh (IS) targets for the week of October 17-October 23," the spokesman for the coalition, Colonel John Dorrian, told AFP.
He said those strikes had destroyed 136 IS fighting positions, 18 tunnels and 26 car bombs.
The offensive, launched on October 17, aims to retake towns and villages surrounding Mosul before elite troops will breach the city and engage die-hard jihadists in street-to-street fighting.
On the eastern side of Mosul, federal troops were battling IS on Monday in Qaraqosh, which used to be the largest Christian town in the country.
Army forces entered the town for the third day running but armoured convoys deployed around it were met with shelling from inside, an AFP correspondent reported.
Federal forces also scored gains on the southern front, where they have been making quick progress, taking one village after another as they work their way up the Tigris Valley.
On the northern front, Kurdish peshmerga forces were closing in on the IS-held town of Bashiqa.
Turkey, which has a base in the area, said Sunday it had provided artillery support following a request from the peshmerga.
The presence of Turkish troops on Iraqi soil is deeply unpopular in Baghdad and the Joint Operations Command on Monday vehemently denied any Turkish participation.
But AFP reporters near Bashiqa said artillery fire coming from the Turkish base had been visible on several occasions since the start of operations a week ago.
While an increasingly pragmatic IS has tended in recent months to relinquish some of its positions to avoid taking too many casualties, US officials said the group was mounting a spirited defence of Mosul.
If IS loses Mosul in Iraq, only Raqa in Syria will remain as the last major city under the jihadists' control in either country.
"They have made a very good job of preparing their defences around the city," one US military official told reporters during Carter's visit.
The official said IS's strategy appeared to be to trade "non-necessary space" around Mosul for casualties among federal and Kurdish ranks.
The coalition estimates the number of IS fighters defending Mosul -- the city where IS supremo Abu Bakr al-Baghdadi proclaimed a "caliphate" two years ago -- at 4,000 to 7,000.
The coalition's top commander, General Stephen Townsend, said Sunday he expected not all the jihadists in Mosul would "fight to the death".
"By targeting the mid-tier leaders, which our special operations forces and air force have done remarkably well, we have caused a lot of confusion" in IS ranks, he said.
"I think it's going to pay off in the coming weeks."
Seeking to distract attention, the jihadists have attempted to hit back with attacks elsewhere in Iraq, including in the remote western town of Rutba on Sunday.
They briefly seized the mayor's office, captured and executed at least five people -- civilians and policemen -- and still controlled two neighbourhoods on Monday, army commanders said.
Two days earlier, IS sleeper cells in Kirkuk joined up with gunmen infiltrating the northern Iraqi city to launch a brazen raid that saw the jihadists attack several government buildings.
The attack sparked clashes that lasted three days as security forces imposed a curfew to hunt down attackers holed up in several buildings across the city.
The provincial governor, Najmeddin Karim, told AFP Monday that the attack was over and life was returning to normal.
He said more than 74 IS militants were killed during the three-day unrest, which left at least 46 other people dead, most of them members of the security forces.