Just days after Islamic State leader Abu Bakr al Baghdadi was killed in Syria, his older sister has reportedly been captured alive in the same country.

Turkey said it had arrested 65-year-old Rasmiya Awad in northwest Syria, with an official describing it as an intelligence gold mine.

She was detained in a raid on a trailer container where she was living with her family.

She was with her husband, daughter-in-law and five children when she was captured near the town of Azaz, which is part of the region administered by Turkey.

The adults are being interrogated, the official said.

Little is known about al Baghdadi’s sister.

The IS leader died in a US raid in the nearby province of Idlib last month.

Baghdadi, 48, fled into a tunnel and killed himself and two children after being tracked down by American special forces.

Meanwhile, Britain’s terror threat level has been lowered from severe to substantial for the first time in five years.

Substantial means a terrorist attack is now likely instead of highly likely.

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The last time the terror threat level was deemed substantial – the middle of five options – was August 2014.

(c) Sky News 2019: ‘Intelligence gold mine’: Sister of killed IS leader captured alive in Syria