Iraqi Kurdish fighters are exchanging heavy fire with ISIL fighters as they advance from two directions on a town held by the armed group just 13km east of the city of Mosul.
The town of Bashiqa has been surrounded by Kurdish Peshmerga forces for weeks.
Monday's push appears to be the most serious yet to drive the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) from the area, which is to the northeast of Mosul, the group's last major urban bastion in the country.
Al Jazeera's Mohammed Jamjoom, reporting from the frontline near Bashiqa, said: "It was the biggest push yet to try to take control of Bashiqa since the battle for Mosul began."
"The Peshmerga fighters are optimistic. They say there are only about 100 to 200 ISIL fighters left, as well as possibly three very high-ranking ISIL commanders," he said, adding that there was black smoke rising from the city and its surrounding areas, signaling ISIL's tactic of burning tyres and oil to limit aerial vision and create suffocating smells.
There were also white plumes of smoke from US-led coalition air strikes over the city, he said.
"As far as civilians go, the Peshmerga fighters believe that most of the civilians have already fled the town."
|The three-week-long Mosul offensive has slowed down in recent days as Iraqi forces have pushed into more densely populated areas of the city [Al Jazeera]
Kurdish forces launched mortar rounds and fired heavy artillery into the town on Sunday in advance of the offensive.
Al Jazeera's Jamal Elshayyal, reporting from Erbil, said: "As far as the Kurdish fighters are concerned, Bashiqa is the last remaining major area ISIL controls in the KRG, which is the semi-autonomous Kurdish region of Iraq."
"[Kurdish forces] are entering [Bashiqa] not only on the ground but from the skies as well. Bashiqa is also important to retake because it has a multicultural, multi-ethnic population, which includes Christians, Yazidis, Sunni Arabs, and many others," he said.
"This is not only a fight against ISIL to retake these towns for the Iraqi government. There's a sectarian side to this conflict where maybe getting these towns back will give some benefit to beating ISIL, as it will build a cross-section of society banded together."
ISIL hits back
The three-week-long Mosul offensive has slowed down in recent days as Iraqi forces have pushed into more densely populated areas of the city.
The Iraqi army has also been fighting in the district of Gogjali, east of Mosul.
The army is going house-to-house to secure some of the other districts taken in recent days.
However, Iraqi troops have been forced to retreat from the neighbourhood of Al-Karamah after ISlL fighters used a network of tunnels to surround them.
Elsewhere, two ISIL suicide attacks killed at least 22 people in cities 200km south of Mosul.
A fighter blew himself up in an ambulance packed with explosives at a checkpoint in Samarra. Ten Iranian pilgrims were among the dead in that attack.
Earlier, another bomber had blown up his vehicle on the outskirts of the city of Tikrit.
"The trajectory of suicide bombings is in correlation with how much closer the Iraqi army is getting to the centre of Mosul," Elshayyal said. "The closer they get, the higher number of suicide and car bombings we will see.
"Over the past few days, ISIL has been focusing all its efforts and firepower on maintaining its stronghold in Mosul. We even saw some videos of international journalists stuck for up to 24 hours as they and the forces they were embedded with were ambushed by ISIL fighters."
Source: Al Jazeera News And Agencies