LILLE, France : Migrant children stuck in slums on France's northern coast face a "permanent danger" of sexual abuse or exploitation, the UN Children's Fund has warned, urging the creation of protected areas for minors.

"They fear going out at night, after dark, for fear of rape," UNICEF said in a hard-hitting report on unaccompanied children titled "Neither Safe nor Sound".

The children's "living conditions..., the violence experienced on the road, the risks of border crossings, the monetary relationships in shantytowns, and forms of the resulting enslavement, constitute a permanent danger" at all seven sites covered in a recent study, UNICEF said. The study, released on Thursday, was carried out between January and April at sites stretching from the Calais area to Normandy where around 500 children live without their parents. The 90-page report drew particular attention to the risk of rape facing young Afghan boys because of the practice known as batcha bazi that allows them to be treated as "sexual objects" by men.

"Batcha bazi is viewed by Afghans as a legitimate practice," the report said. "According to the migrants we interviewed, these practices result in the rape of young boys being seen as more socially acceptable than that of girls."

Female minors risk sexual abuse or being lured into prostitution to raise money to enter some of the camps or to cross the Channel, which costs between 5,000 and 7,000 euros ($5,600 and $8,000), the report said.

"The situation in which (the children) find themselves shows evidence of a series of violations of the Convention on the Rights of the Child," the report said, noting that both France and Britain are signatories of the 1990 UN treaty.

"All the children interviewed... complained of cold and fatigue," it said. "The most vulnerable among them were living in shelters that were very much exposed to the elements and had difficulty in accessing the distributed meals as well as showers."

The minors also said they suffered "recurring nightmares, anxiety problems, nervousness and aggressiveness," it said, adding that they are increasingly seeking psychiatric care.

The study decried the lack of facilities for minors and a "lack of coordination" between government and volunteer actors.

Among the study's recommendations were the creation of protected areas in the slums that are "secure and specific to unaccompanied children"; "regular training" regarding child protection for all those involved; and an emphasis on reuniting the minors with their families.