Turkey has captured a wife of Abu Bakr al-Baghdadi, President Tayyip Erdogan said on Wednesday, more than a week after the former Islamic State leader killed himself during a raid by U.S. Special Forces.

"The United States said Baghdadi killed himself in a tunnel. They started a communication campaign about this," Erdogan said in a speech at Ankara University. "But, I am announcing it here for the first time: We captured his wife and didn't make a fuss like them. Similarly, we also captured his sister and brother in law in Syria."

A senior Turkish official said on Monday that Turkey had also captured Baghdadi's sister, her husband and daughter in the northern Syrian town of Azaz.

Rasmiya Awad, 65, was detained in a raid near Azaz, the official said, referring to a Turkish-controlled Syrian town near the border. 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.

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

Baghdadi killed himself last month when cornered in a tunnel during a raid by U.S. special forces in northwestern Syria. Islamic State, in an audio tape posted online on Thursday, confirmed that its leader had died and vowed revenge against the United States.

Erdogan's communications director said the woman's capture was evidence of Turkey's determination to fight against Islamic State.

"The arrest of al-Baghdadi's sister is yet another example of the success of our counter-terrorism operations," Fahrettin Altun wrote on Twitter early on Tuesday.

"Much dark propaganda against Turkey has been circulating to raise doubts about our resolve against Daesh," he wrote, using another name for Islamic State.

"Our strong counter-terrorism cooperation with like-minded partners can never be questioned."

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 2014-2017 before Islamic State's control was wrested away by U.S.-led coalition forces including Iraqis and Syrian Kurds.

The group, also known as ISIS, said a successor to Baghdadi identified as Abu Ibrahim al-Hashemi al-Quraishi had been appointed. A senior U.S. official last week said Washington was looking at the new leader to determine where he came from.

World leaders welcomed his 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.