A 17-year-old Australian boy detained in a Syrian prison from where he sent voice messages begging for help has been released.

Save the Children says it has learned of the boy’s release from limited communication with his family.

The boy is in the custody of the US-backed Syrian Democratic Forces (SDF) and coalition forces.

At least 200 prison inmates and militants and 30 security forces have been killed since Islamic State militants attacked the jail last week in a bid to free their members held there, officials have said.

The Kurdish-led SDF, with US air support, this week regained control of the prison in the northeastern Syrian city of Hasaka.

Save the Children still holds fears for the boy’s safety, saying he still requires medical treatment, which is an issue in SDF custody.

The organisation has called on the Australian government to step in and act before an Australian child dies, saying he hasn’t yet received any medical assistance.

In the recorded messages from when he was in the Guweiran prison, the boy said he was bleeding from bullet wounds.

“I just got shot by Apache (helicopter), my head is bleeding, I have injured my head and my hand,” he says.

“I need help, we’re getting hit from every side from the Kurds, we’re getting hit by planes.”

Middle Eastern media organisation Al Jazeera reported SDF commandos closed in on the Syrian prison on Wednesday and captured Islamic State fighters.

At least 550 suspected IS fighters surrendered to the US-backed forces as they wrestled back control of the prison, the outlet reported.

The home affairs department has been contacted for comment following the boy’s release from the prison.

– AAP