The older sister of the slain leader of Islamic State (ISIS), Abu Bakr al-Baghdadi ,has been captured in northwestern Syria during a raid on Monday, according to a senior Turkish official who called the arrest an intelligence "gold mine."

Rasmiya Awad, 65, is suspected of being affiliated with the extremist group, the Turkish official said without elaboration.

Rasmiya Awad, the older sister of the slain leader of Islamic State (ISIS), Abu Bakr al-Baghdadi, has been captured in northwestern Syria during a raid on Monday, according to a senior Turkish official who called the arrest an intelligence "gold mine." (Reuters)

"This kind of thing is an intelligence gold mine,” said the official, speaking on condition of anonymity in line with government protocols. “What she knows about [ISIS] can significantly expand our understanding of the group and help us catch more bad guys."

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Awad was captured in a raid Monday evening at a trailer container in which she was living with her family near Azaz, in Aleppo Province. That's part of the region administered by Turkey after it carried out a military incursion to chase away ISIS militants and Kurdish fighters.

Awad was with her husband, daughter-in-law and five children at the time of the capture, the official said, adding that the adults are being interrogated.

This file image made from a video posted on a militant website in April 2019 purportedly shows former ISIS leader Abu Bakr al-Baghdadi. (AP/Al-Furgan media)

Last month, Awad’s brother, Baghdadi, an Iraqi from Samarra, was killed in a raid by U.S. troops at an ISIS compound in the nearby Syrian province of Idlib. Video footage of the raid was released on Wednesday by the Pentagon.

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A DNA test confirmed Baghdadi’s identity before he was later buried at sea, President Trump said last week.

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

Islamic State spokesman Abu Hassan al-Muhajir, considered a potential successor to Baghdadi, was himself killed in northwestern Syria in a separate attack by U.S. forces, a senior State Department official confirmed to Fox News last week.

Baghdadi’s successor was named days later and is said to be a scholar, well-known warrior and “emir of war,” the terrorist group revealed.

In audio released by the ISIS central media arm, al-Furgan Foundation, on Thursday, the terrorist group confirmed Baghdadi’s death and named his successor as Abu Ibrahim al-Hashimi al-Qurayhi.

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Not much else is known about his successor or how the group's structure has been affected by the series of jolts.

Fox News’ Lucia Suarez and The Associated Press contributed to this report.