Thousands of Iraqis continued to stream into the country's Kurdish region, as government forces prepare for a ground offensive in a northern area controlled by the Islamic State of Iraq and the Levant (ISIL, known as ISIS) group.

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.

IN PICTURES: The final push to retake Mosul from ISIL

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.

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.

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.

Coalition air raids have started targeting ISIL fighters in the city, just one month after securing victory in Mosul, but the ground invasion is yet to start.

Al Jazeera's Osama Bin Javaid, reporting from the Khazar camp, said that 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.

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

'Ready enough' for Tal Afar

In 2014, before ISIL took control of the city, Tal Afar had a population of around 200,000.

On Friday, senior US military leaders said a ground assault by Iraqi forces on the ISIL-held city would be "unfolding relatively soon".

"I can't say that we replaced every single damaged or broken vehicle or rifle or machine gun," said Lieutenant General Stephen Townsend, the top US commander in Iraq. But, he said: "They'll be ready enough."

The upcoming fight follows weeks of Iraq regrouping troops and repairing equipment and weapons after recapturing Mosul in July.

Mosul took a heavy toll on Iraqi forces, with as many as 1,400 troops killed and more than 7,000 wounded.

Iraqi military leaders said Prime Minister Haider al-Abadi has approved their combat plans.

The fight will involve a broad spectrum of forces, including the Iraqi army, counterterrorism troops, police and a group of mainly Shia, Iranian-backed militias.

The fight will start "in the next few days," Iraqi Brigadier General Yahia Rasool told reporters.

Speaking through an interpreter, he said officials believe there are between 1,400 and 1,600 ISIL fighters in the Tal Afar area, many, foreign fighters.

Rasool said the various Iraqi forces have already largely encircled Tal Afar.

"I don't think it will be tougher than the battle of Mosul, taking into consideration the experience we got in Mosul," he said.