Spokesman Farhad Shami said all Islamic State militants had surrendered hours after 500 had given themselves up following clashes in some buildings.

It comes a week after a breakout by Islamic State prisoners left dozens dead, as IS fighters used vehicles and explosives to ram through the prison walls before entering the building with heavy machine guns.

Fears grow for 850 children trapped inside prison seized by Islamic State

At least 200 prison inmates and militants and 30 security foces have died in the process.

There has been no update yet on the 850 children and minors - who lived alongside the nearly 5,000 prisoners in the overcrowded jail and are nicknamed "cubs of the caliphate" - that have been caught in the crossfire.

One audio recording sent to the Associated Press from a 17-year-old Australian boy inside the prison sees him appealing for help, saying he was injured and bleeding.

The boy said his friends had been killed and he had seen bodies of kids aged eight to 12.

The UN and international aid organisations have expressed concern for their lives.

"It's very hard to even imagine what atrocities these children are witnessing," Juliette Touma, from UNICEF, said previously.

The Syrian Democratic Forces (SDF), aided by US troops, began to storm the prison on Monday.

British Special Forces and the US military had been involved in the operation to retake the prison, sources told Sky earlier this week.

Al-Sina'a is the largest prison facility where the SDF has kept thousands of detainees. The relatives of many say they were arrested on flimsy charges for resisting the SDF's forced conscription.

The Kurdish-led militia denies this.

Analysis: Islamic State slowly showing signs of growing stronger after prison raid

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The fighting has also forced more than 45,000 civilians - mostly women and children - to flee their homes.

The prison's inmates were all detained during the US-backed campaigns that drove IS from its last territorial enclave in Syria, back in 2019.