Federal forces and Kurdish peshmerga fighters gained ground 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 yesterday near the Jordanian border.
Following a weekend visit to Iraq by US Defence Secretary Ashton Carter, American officials said the coalition was providing the most air support yet to the operation.
"There were 32 strikes with 1,776 munitions delivered" against IS targets between October 17 and 23, coalition spokesman Colonel John Dorrian told AFP.
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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 breach the city and engage die-hard jihadists in street-to-street fighting.
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 yesterday it had provided artillery support following a request from the peshmerga.
But AFP reporters near Bashiqa said artillery fire coming from the Turkish base had been sighted 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.
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