Washington: US officials claimed on Friday that American aid worker Kayla Mueller, who died earlier this year while being held hostage by Islamic State militants, was raped several times by the group's leader Abu Bakr al-Baghdadi while she was held hostage by Sunni militant group in Syria.

The officials confirmed a report by ABC News, which claimed that Mueller, 26,was repeatedly raped by al-Baghdadi.

The officials did not reveal their identity but the White House declined to comment. "We were told Kayla was tortured, that she was the property of al-Baghdadi. We were told that in June by the government," Kayla's parents, Carl and Marsha Mueller, were quoted as telling ABC News.

In February, Islamic State had said that Mueller, of Prescott, Arizona, was killed when Jordanian fighter jets bombed a building where she was being held outside Raqqa, a stronghold in Syria of the Islamist militant group. But doubts were raised over her death by Jordanian and U.S. officials.

Mueller remained in IS' captivity for 18 months after being taken hostage in August 2013 while leaving a hospital in Aleppo in northern Syria.

Al-Baghdadi decided to bring Mueller to be imprisoned inside the home in Syria of Abu Sayyaf, a Tunisian Islamic State member who was killed in a U.S. raid in May, counter-terrorism officials told ABC News.

The information about the role played by al-Baghdadi in the captivity and sexual abuse of Mueller was drawn from many sources including U.S. interviews with at least two teenage Yezidi girls held as sex slaves in Sayyaf's compound and the interrogation of Sayyaf's wife, Umm Sayyaf, who was detained by U.S. forces in the raid in which her husband was killed, ABC News quoted the officials as saying.