by Abu Bakr al-Baghdadi

US hostage Kayla Mueller was raped repeatedly by Abu Bakr al-Baghdadi, the self-proclaimed caliph of the Islamic State jihadist group, before her death, US television reported.

Top IS leader Baghdadi personally brought the 26-year-old aid worker to be imprisoned inside the home of the group's top financier, ABC News reported.

The television network quoted US counter-terrorism officials and spoke to Mueller's parents, who confirmed being told by government officials that their daughter was sexually assaulted by Baghdadi.

"We were told Kayla was tortured, that she was the property of al-Baghdadi. We were told that in June by the government," Carl and Marsha Mueller told ABC News.

The Iraqi extremist regularly visited the compound to meet his financial lieutenant, Abu Sayyaf, and to sexually assault Mueller, ABC said.

IS fighters claimed Mueller, who was kidnapped in the Syrian city of Aleppo in August 2013, was killed in a February 6 coalition air strike that buried her in rubble.

US officials say the circumstances of her death remain unclear.

US hostage Kayla Mueller was raped repeatedly by Abu Bakr al-Baghdadi, the self-proclaimed caliph of the Islamic State jihadist group, before her death, US television reported.

Top IS leader Baghdadi personally brought the 26-year-old aid worker to be imprisoned inside the home of the group's top financier, ABC News reported.

The television network quoted US counter-terrorism officials and spoke to Mueller's parents, who confirmed being told by government officials that their daughter was sexually assaulted by Baghdadi.

"We were told Kayla was tortured, that she was the property of al-Baghdadi. We were told that in June by the government," Carl and Marsha Mueller told ABC News.

The Iraqi extremist regularly visited the compound to meet his financial lieutenant, Abu Sayyaf, and to sexually assault Mueller, ABC said.

IS fighters claimed Mueller, who was kidnapped in the Syrian city of Aleppo in August 2013, was killed in a February 6 coalition air strike that buried her in rubble.

US officials say the circumstances of her death remain unclear.