About 1,500 children are being detained by federal and Kurdish authorities in Iraq for alleged links to the Islamic State group, Human Rights Watch says.
A new report says the children are often arbitrarily arrested and tortured to force confessions.
HRW urges the federal and Kurdistan Region's governments to amend anti-terrorism laws to end such detentions, saying they violate international law.
Iraqi and Kurdish officials have so far made no comment.
The Kurdistan Region's government has previously rejected an HRW report which alleged that children were being tortured to confess to IS links.
In January, an official said its policy was to "rehabilitate" such children; torture was prohibited; and children were afforded the same rights as other prisoners.
What does the report say?
The 53-page report says that at the end of 2018 the Iraqi and Kurdish authorities were holding about 1,500 children for alleged IS links.
At least 185 foreign children have been convicted on terrorism charges and sentenced to jail terms, HRW cites the Iraqi government as saying.
The report alleges that the local authorities:
- Often arrest and prosecute children with any perceived connection to IS
- Use torture to coerce confessions
- Sentence suspects in hasty and unfair trials
"This sweeping, punitive approach is not justice, and will create lifelong negative consequences for many of these children," said Joe Becker, children's rights advocacy director for HRW.
What do the children say?
Last November, HRW interviewed 29 children held for alleged IS affiliation.
It says 19 of them reported that they had been tortured, including beatings with plastic pipes, electric cables or rods.
A 17-year-old boy detained by Iraqi security forces in 2017 said he was beaten on the soles of his feet and repeatedly suspended by his wrists for 10 minutes at a time by interrogators. They told him that he should confess to joining IS for three days, which he eventually did, according to the report.
After his trial he was transferred to a prison at Baghdad airport, where he remained for seven-and-a-half months.
"Every day was torture. We were beaten every day, all of us," he said.
One 14 year old said he was tortured into making a confession by officers from the Kurdish Asayish police force in 2017.
"They were beating me all over my body with plastic pipes," he said.
"First they said I should say I was with IS, so I agreed. Then they told me I had to say I worked for IS for three months. I told them I was not part of IS, but they said, 'No, you have to say it.'"
The report also points out that most of those interviewed said they had joined IS because of economic need, peer or family pressure.
Some cited family problems or a desire to gain social status.
HRW says that those Iraqi children who have been released are afraid to return home because of the stigma of IS membership and a threat of reprisals.
The human rights group stresses that international law recognises children recruited by armed groups primarily as victims who should be rehabilitated and reintegrated into society.