They originally hailed from Hawija in northern Iraq, but took refuge in Hammam al-Alil camp, about 150 kilometres (100 miles) further north, during Iraq's battle against the Islamic State group.

Early Wednesday, Iraqi officials and security forces began guiding residents of the camp in Nineweh province to more than a dozen white buses bearing the emblem of Iraq's transport ministry.

"We are being returned to our areas. Maybe I'll have to live in a camp there because my house is destroyed," said Umm Hikm, a 65-year-old displaced woman who had been living in the camp for two years.

"We don't know what will happen to us."

Women in black robes with young children and their meagre belongings queued by the buses, some of them crying, as officials checked their names against a list of those expected to leave.

More than 150 families, or around 550 individuals, are to be returned to Kirkuk province as part of the transfer, said Ali Khodr, province's top official dealing with displacement.

"A few days ago, 35 families were returned to (the western province of) Anbar. We are working on returning the rest of the displaced to their provinces of origin," he told AFP.

"We have 4,500 families from various provinces outside Nineweh... These families (should) return to their areas so the local governments can help them," he added.

More than 1.6 million people remain displaced in camps, unfinished structures or rented apartments across Iraq nearly two years after the country declared victory over IS.

The government has stressed its policy is for all those displaced to return home and for the camps to be shut, but many of their areas of origin remain heavily damaged and lack services.

- 'Opening new wounds' -

After several hours in Iraq's baking sun, the buses left for Hawija, according to the Norwegian Refugee Council (NRC) which manages Hammam al-Alil and was monitoring the transfers.

NRC's Iraq media coordinator Tom Peyre-Costa said the group was very concerned about the process, as the displaced often had no homes to return to and feared retaliation from their communities for perceived ties to IS.

"They are scared, and most families from Hawija leaving today are undocumented," he said, speaking by phone from the camp.

"Going home without documents means they will not have access to anything -- children won't be able to go to school, no access to health care, no food distribution."

Amnesty International on Wednesday called the returns "premature" and urged Iraqi authorities to halt them immediately.

"The Iraqi authorities have always assured Amnesty International that any returns they carry out are voluntary," said the rights group's regional research director Lynn Maalouf in a statement.

"This sudden change in policy is worrisome and is contrary to international human rights law and standards, as well as to international humanitarian law."

NRC's Peyre-Costa urged the government to make sure areas of origin were safe for returnees and to prioritise reconciliation efforts to heal lingering resentment from the fight against IS.

"There is a feeling here that they want to heal the wounds of the conflict too fast -- and by doing this they are opening new wounds," he said.