Children escaping Syria's Raqqa have been "tormented" by years of living under jihadist rule culminating in a ferocious bombing campaign on the city, a charity said on Monday.
It could take decades for young people from ISIL's stronghold to overcome their psychological injuries, Save the Children warned.
The NGO interviewed children and their families who escaped the war-torn city, where a US-backed assault is battling to defeat ISIL.
"Raqqa's children might look normal on the outside but inside many are tormented by what they've seen," said the NGO's Syria director Sonia Khush.
"The children of Raqqa didn't ask for the nightmares and memories of seeing loved ones die right in front of them."
Raashida, 13, fled with her family three months ago to a displacement camp north of Raqqa.
"ISIL beheaded people and left their bodies on the ground. We saw this and I couldn't handle it," she said.
"I wanted to sleep but I couldn't when I remembered what I saw. And I wouldn't sleep - I would stay awake because of how scared I was."
Since ISIL overran Raqqa in early 2014, the city became synonymous with the group's horrifying practices: public beheadings, stonings and jihadist propaganda in schools.
Raashida's father Aoun said he tried to keep his children away from such sights, but they slowly became accustomed to the macabre scenes.
"There is nothing called 'children' anymore, we are all in a living hell now," he said.
Up to 25,000 people - almost half of them children - remain trapped in Raqqa as US-backed forces tighten the noose on ISIL.
Save the Children warned that heavy coalition bombardment left families "facing an impossible decision: stay and risk being bombed or leave and risk being shot at by ISIL or stepping on a landmine".
Yaacoub, his nine siblings, and their parents came under ISIL sniper fire as they made the perilous journey out three months ago.
The 12-year-old and his siblings described ISIL punishments such as stonings, cutting off smokers' fingers and sewing mouths shut.
"They filled the roundabout with heads that had been cut off. We saw them doing it, and cutting off hands," Yaacoub said.
His younger brother Fuad, two, was wounded in an air strike.
Monitors have said hundreds of civilians have been killed in coalition raids since the Arab-Kurdish alliance it backs broke into Raqqa in early June.
The UN has called for a pause in fighting to allow remaining civilians to flee.
Save the Children backs safe routes for children and families, but said that was just the beginning of a longer process to ensure their mental well-being too.
"It's crucial that the children who've made it out alive are provided with psychological support to help them deal with the trauma of witnessing senseless violence and brutality," said Ms Khush.
"We risk condemning a generation of children to a lifetime of suffering unless their mental health needs are addressed."
