Turkey captured the elder sister of the slain leader of the Islamic State group in northwestern Syria on Monday, according to a senior Turkish official, who called the arrest an intelligence "gold mine."

Key points: Rasmiya Awad was captured in a raid on a trailer she was living in with her family in Aleppo province

Rasmiya Awad was captured in a raid on a trailer she was living in with her family in Aleppo province They say she will be able to significantly expand what they know about the operations of IS

They say she will be able to significantly expand what they know about the operations of IS But experts question how much useful intelligence she will be able to provide

Little is known about the sister of Abu Bakr al-Baghdadi. The Turkish official said the 65-year-old known as Rasmiya Awad is suspected of being affiliated with the extremist group. He did not elaborate.

Awad was captured in a raid on a trailer container she was living in with her family near the town of Azaz, in Aleppo province on Monday evening.

The area is part of the region administered by Turkey after it carried out a military incursion to chase away IS militants and Kurdish fighters. Allied Syrian groups manage the area known as the Euphrates Shield zone.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 42 seconds 42 s The Pentagon released video of the al-Baghdadi raid

The official said the sister was with her husband, daughter-in-law and five children.

The adults are being interrogated, he said, speaking on condition of anonymity in line with government protocol.

"This kind of thing is an intelligence gold mine. What she knows about [IS] can significantly expand our understanding of the group and help us catch more bad guys," the official said.

But experts have questioned how much useful intelligence Awad could provide.

Mike Pregent, a counter-terrorism expert at the Hudson Institute, told the BBC that he did not believe she would be aware of "imminent attack plans" but may know smuggling routes.

"She might know networks that Baghdadi trusted, people that he trusted, networks in Iraq that helped her facilitate her own travel and her family's travel," he told the BBC.

"This should be able to give our US intelligence and other allied intelligence officers a view into [IS] networks and how they moved family members, how they travelled and who they trusted."

Baghdadi, an Iraqi from Samarra, was killed in a US raid in the nearby province of Idlib last month.

The raid was a major blow to the group, which has lost territories it held in Syria and Iraq in a series of military defeats by the US-led coalition and Syrian and Iraqi allies.

Abu Bakr al-Baghdadi was killed in a raid near Idlib last month. ( AP: Al-Furqan media )

Many IS members have escaped through smuggling routes to north-western Syria in the final days of battle ahead of the group's territorial defeat earlier this year, while others have disappeared into the desert in Syria or Iraq.

The reclusive leader Baghdadi was known to be close to one of his brothers, known by his nom de guerre Abu Hamza.

Baghdadi's aide, a Saudi, was killed hours after the raid, also in north-western Syria, in a US strike.

The group named a successor to Baghdadi days later — Abu Ibrahim al-Hashimi al-Qurayshi — but little is known about him or how the group's structure has been affected by the successive blows.

A senior US official last week said Washington was looking at the new leader to determine where he came from.

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