Iraqi forces have launched a ground offensive to retake a key ISIL-held area in the northern part of the country, Prime Minister Haider al-Abadi said.

“You either surrender, or die”, Abadi said in a televised speech announcing the operation early on Sunday.

He was addressing Islamic State of Iraq and the Levant (ISIL, also known as ISIS) fighters, who have been in control of the city since 2014.

Tal Afar and the surrounding area are among the last pockets of ISIL-held territory in Iraq, after victory was declared in Mosul, the country’s second-largest city.

Al Jazeera’s Osama Bin Javaid, reporting from Erbil, said that while the ground offensive has just been announced, “the operation has really been underway for the last few weeks”.

US-led coalition air strikes have been started targeting ISIL fighters in the city, just one month after securing victory in Mosul.

“In the last 48 hours, they’ve picked up that activity and destroyed a number of ISIL targets,” Bin Javaid said.

Iraq who controls what infographic

Tal Afar is west of Mosul and about 150km east of the Syrian border, sitting along a major road that was a key ISIL supply route.

It was cut off from the rest of ISIL-held territory in June.

Thousands flee

Hours before Abadi’s announcement, the Iraqi air force dropped leaflets over the city, telling the population to take precautions.

“Prepare yourself, the battle is imminent and the victory is coming,” they read.

Iraqi officials believe there are between 1,400 and 1,600 ISIL fighters in the Tal Afar area, including many foreign fighters, according to Iraqi Brig. Gen. Yahia Rasool who spoke through an interpreter on Saturday.

“I don’t think it will be tougher than the battle of Mosul, taking into consideration the experience we got in Mosul,” he told reporters.

Retired US General Mark Kimmitt said that while retaking Tal Afar would be an “important milestone”, it would not mean final days for ISIL.

“We’re not looking at the final days of ISIS, either in Iraq or in Syria, or outside of those countries,” Kimmitt told Al Jazeera. “It still remains a very, very potent force, not only in the self-proclaimed caliphate, but we continue to see ISIS-inspired attacks in places such as Barcelona and elsewhere.”

READ MORE: ISIL’s smouldering footprint in Qayyara

Thousands of Iraqis have fled to Iraq’s Kurdish region as preparations of the offensive continued.

The Norwegian Refugee Council said on Saturday that refugees near the northern city of Tal Afar were faced with harsh conditions, and were stopped by authorities in east of Mosul and Kurdish areas as they tried to flee the fighting.

“It’s very hard for them to move through,” Melany Markham, a spokesman of the humanitarian group, told Al Jazeera, adding that one transit site was already at full capacity, and could not take more refugees.

She said that temperatures in the height of summer of between 45 and 50 degrees Celcius make journeys even more challenging.

Markham said that while their transit site in Hammam al-Alil is full, other camps such as in Khazar, west of the Kurdish city of Erbil, could accommodate up to 40,000 refugees.

An estimated 50,000 people have fled the areas surrounding Tal Afar since April, and at least 50,000 more could flee in the coming days and weeks, according to aid groups.

That number is in addition to the estimated one million refugees who have fled Mosul.

Source: Al Jazeera and news agencies