An Australian teenager is believed to have died in a Syrian jail after being held for three years, his family said Monday as they pleaded for the return of other detained women and children.
Yusuf Zahab, 17, died from "uncertain causes" in northeast Syria at the Al-Sinaa prison, Human Rights Watch said.
Kurdish-led forces have held Islamic State suspects at the prison, which was the site of intense fighting between IS fighters and US-backed troops earlier this year.
"We are heartbroken and angry," Zahab's family said in a statement released by HRW.
"Yusuf didn't need to die. The previous Australian Government knew about Yusuf's predicament for more than three years," they added.
Born in Sydney, Zahab was 11 when he was taken to Syria by relatives before being detained by Syrian Democratic Forces in 2019.
He had previously begged for help in audio messages released by the human rights group, and described watching fellow child prisoners being killed in front of him during a raid on the prison.
"There's a lot of bodies, dead bodies, and there's a lot of injured people screaming from pain," he had said.
Australia's Department of Foreign Affairs said it was still seeking to confirm the death but was offering consular assistance to the family.
"The Australian Government remains deeply concerned about the situation of Australians in northeast Syria, including the welfare of those detained in prisons and other detention centres," a department spokeswoman said in a statement.
Western countries have faced a dilemma on how to handle their citizens detained in Syria since the end of military operations against the Islamic State group in 2019.
Thousands of extremists joined the group as fighters, often bringing their wives and children to live in the "caliphate" Islamic State declared in territory it conquered in Iraq and Syria.
According to HRW, more than 41,000 foreign citizens - the majority under 12 years old - are being held in camps and prisons in northeast Syria over alleged IS links.
A spokeswoman for Australian detainees' families said that up to 80 Australian nationals - including 19 women and 29 children - are among them.
Zahab family pleaded with the Australian government to act.
"Please repatriate the remaining Australian women and children. Please act before another life is lost," the family said in a statement.
HRW associate crisis and conflict director Letta Tayler accused Australia and other foreign governments of having "outsourced responsibility" for their nationals left in "horrific conditions".
Zahab's death "should prompt these countries to urgently bring their detained citizens home," Tayler said.