Hundreds of women and children were captured during the group’s bloody sweep through northern Iraq earlier this year and have since been trafficked as sex slaves , forced into marriage and imprisoned.

Victims who managed to escape told Amnesty International that many Yazidi girls killed themselves after losing hope of being saved.

A 20-year-old survivor, called Luna, said she was held with 20 girls as young as 10 in the Isis-controlled city of Mosul when they were told to dress up.

“One day we were given clothes that looked like dance costumes and were told to bathe and wear those clothes,” she added. “Jilan killed herself in the bathroom. She cut her wrists and hanged herself. She was very beautiful.

“I think she knew that she was going to be taken away by a man and that is why she killed herself.”

Another woman, 27-year-old Wafa, said she and her sister attempted suicide while imprisoned in Mosul after the man holding them gave them the choice of marrying him and his brother or being sold as slaves.

“At night we tried to strangle ourselves with our scarves,” she told Amnesty. “Two girls who were held with us woke up and stopped us and then stayed awake to watch over us.

“When they fell asleep at 5am we tried again, and again they woke up and stopped us. I could not speak for several days after that.”

Relatives of girls who managed to escape fear that the trauma will never leave them, reporting panic attacks and depression.

The grandfather of a 16-year-old girl who was raped in Isis captivity said: “She is very sad and quiet all the time. She does not smile anymore and seems not to care about anything. I worry that she may try to kill herself, I don’t let her out of my sight.”

Amnesty interviewed 42 women and girls for its report, “Escape from Hell”, which is being released today.

It chronicles the torture, rape and sexual violence suffered by women from the Yazidi minority. Women who converted to Islam were forced to marry Isis militants and those maintaining their faith have been trafficked as sex slaves, abused and imprisoned.

Videos have emerged online of horrifying “slave auctions” of girls in Mosul and Isis members have boasted of the abductions, justifying them by calling Yazidis “apostates”.

Thousands of people from the religious minority, who are viciously targeted by the Sunni extremist group because they are considered heretics, were driven from their homes in Sinjar by the Isis advance in August.

Hundreds were killed in raids on towns and more died of thirst or starvation after fleeing up the remote Mount Sinjar.

Randa, a 16-year-old girl from a village near the mountain, was abducted with scores of her family members including her heavily-pregnant mother and given to a man twice her age who raped her.

“Da’esh [Islamic State] has ruined our lives … What will happen to my family? I don’t know if I will ever see them again.”

One woman called Alba, 19, was visibly pregnant with her second child when she was kidnapped with her son but Isis showed no mercy.

“I had my little boy with me and my pregnancy was very visible already but one of the guards chose me to be his wife,” she told Amnesty, adding that the man threatened to send her to Syria if she resisted.

Some Yazidi girls forced into marriage have reported being taken to the homes of Isis fighters’ families and even meeting their wives and children. Some received further abuse, while others made friends with their captor’s wives.

Several girls held by foreign fighters told Amnesty International their families helped them escape and one 13-year-old girl, who was held with her toddler sister, said her captor did not abuse them but instead sent them straight home to their family.

But even those escaping have a bleak prospect to return to, with the loss of dozens of killed or captured relatives, and home towns and villages overrun by Isis.

The trauma of survivors of sexual violence is further exacerbated by the stigma surrounding rape. Survivors feel that their “honour” and that of their families has been tarnished and fear that their standing in society will be diminished as a result.

Donatella Rovera, who spoke to more than 40 former captives in northern Iraq for Amnesty International, said Isis were using rape as a weapon in attacks “amounting to crimes against humanity”.

“The physical and psychological toll of the horrifying sexual violence these women have endured is catastrophic,” she added. “Many of them have been tortured and treated as chattel. Even those who have managed to escape remain deeply traumatised.”

She called on Kurdistan Regional Government, UN and humanitarian organizations to ensure they were reaching everyone who needed support.