Internally displaced persons clear a checkpoint in Qayara, some 50 kilometers south of Mosul, Iraq, Wednesday, Oct. 26, 2016. Islamic State militants have been going door to door in farming communities south of Mosul, ordering people at gunpoint to follow them north into the city and apparently using them as human shields as they retreat from Iraqi forces. Witnesses to the forced evacuation describe scenes of chaos as hundreds of people were driven north across the Ninevah plains and into the heavily-fortified city, where the extremists are believed to be preparing for a climactic showdown. (AP Photo/Marko Drobnjakovic)
Internally displaced persons clear a checkpoint in Qayara, some 50 kilometers south of Mosul, Iraq, Wednesday, Oct. 26, 2016. Islamic State militants have been going door to door in farming communities south of Mosul, ordering people at gunpoint to follow them north into the city and apparently using them as human shields as they retreat from Iraqi forces. Witnesses to the forced evacuation describe scenes of chaos as hundreds of people were driven north across the Ninevah plains and into the heavily-fortified city, where the extremists are believed to be preparing for a climactic showdown. (AP Photo/Marko Drobnjakovic) Credit: ap photograph

Qayara, Iraq — Islamic State militants have been going door to door in villages south of Mosul, ordering people at gunpoint on a mileslong trek into the city and using them as human shields as the extremists prepare to defend it from Iraqi forces, according to residents swept up in the forced evacuations.

Witnesses described scenes of chaos over the past week as hundreds of people were ordered out of their homes without having time to pack and driven north across the Ninevah plains toward the heavily-fortified city, where Islamic State has been preparing for a climactic showdown.

“IS took all of us from our homes at gunpoint and told us they were taking us with them to Mosul,” Ahmed Bilal Harish told The Associated Press on Wednesday. “They said if you don’t come with us you’re an unbeliever.”

He said he and his family were only able to escape when a volley of airstrikes caused the fighters to scatter during the 25-mile forced march from their home in the town of Shura to Mosul.

“We had two choices: We could be killed by Daesh or die along the way, so we ran,” he said, using an Arabic acronym for Islamic State. The family is now living in a camp for those displaced by the fighting in an area under government control.

Other Shura residents also described being forcibly relocated to Mosul over the weekend. The militants only gave people a few minutes to leave and said any stragglers risked being punished for hiding out and trying to join the Iraqi security forces.

One family was forced to leave their home in the middle of a meal, and another lost track of two relatives during the melee and have not seen them since. At least one villager died of a heart attack on the road, they said. The displaced residents spoke on condition of anonymity because of fears for their safety while living under Islamic State rule in Mosul.

Brig. Gen. Alaa Mehsin, of the Iraqi army’s 15th Division, said the Islamic State militants were pulling back to bolster their defenses in Mosul ahead of the coming Iraqi offensive to retake the city. He said they were taking hundreds of civilians as human shields and had planted explosive booby-traps to slow the advancing troops.

“These small villages are secondary to them. Mosul is much more important,” Mehsin said as he strode between maps in an operations center in Qayara, one of the main staging bases for the offensive. “They don’t want to waste their energy.”

The U.N. High Commissioner for Human Rights said Islamic State fighters have been sweeping through the hardscrabble towns and villages to the south of Mosul over the past week, killing those they fear may rise up against them and forcibly relocating others.

In one village south of Mosul, Iraqi forces found the bodies of 70 residents who had been gunned down, and Islamic State appears to have killed 50 former Iraqi police officers it was holding in a building near the city, Rupert Colville, a spokesman for the U.N. agency, told reporters in Geneva.

Iraqi forces have been pushing toward Mosul from several directions since the operation began Oct. 17. It is expected to take weeks, if not months, to retake Iraq’s second-largest city, which fell to the extremists in a matter of days when they swept across northern and central Iraq in the summer of 2014.