Turkey claims to have captured the sister of killed Isis leader Abu Bakr al-Baghdadi and is interrogating her and her husband and daughter-in-law, who were also detained.

A senior Turkish official told Reuters that Rasmiya Awad, 65, was seized on Monday during a raid near the Turkish-controlled northern Syrian town of Azaz. When captured, she was also accompanied by five children.

“We hope to gather a trove of intelligence from Baghdadi’s sister on the inner workings of Isis,” the official said.

Picture provided by Turkish officials of who they say is Rasmiya Awad, the sister of slain Isis leader Abu Bakr al-Baghdadi. Photograph: Turkish Security Officials/Reuters

Little independent information is available on Baghdadi’s sister and Reuters was not immediately able to verify if the captured individual was her.

Fahrettin Altun, the communications director of Turkish president Tayyip Erdoğan, called the arrest “yet another example of the success of our counter-terrorism operations”.

“Our determination to bring justice to those who seek to terrorize our people and destabilize our region cannot be questioned,” he wrote on Twitter. “We have been leading in the fight against terrorism in all its forms.”

Baghdadi killed himself last month when cornered in a tunnel during a raid by US special forces in north-western Syria. Isis confirmed in an audio tape posted online on Thursday that its leader had died and vowed revenge against the US.

Baghdadi had risen from obscurity to lead the ultra-hardline group and declare himself “caliph” of all Muslims, holding sway over huge areas of Iraq and Syria from 2014 to 2017 before control was wrested away by US-led coalition forces including Iraqis and Syrian Kurds.

Isis said a successor to Baghdadi identified as Abu Ibrahim al-Hashimi al-Qurayshi had been appointed. A senior US official last week said Washington was looking at the new leader to determine where he came from.

World leaders welcomed Baghdadi’s death, but they and security experts warned that the group, which carried out atrocities against religious minorities and horrified most Muslims, remained a security threat in Syria and beyond.