US mourns death of IS hostage Kayla Mueller

Led by US President Barack Obama, Americans on Tuesday mourned the death of its citizen Kayla Jean Mueller, who was taken hostage in Syria by the Islamic State group.

The 26-year-old aid worker from Arizona, who was captured in August 2013 in Aleppo, worked with humanitarian organisations to help people in need especially those suffering from HIV/AIDS in several countries, including India.

"Kayla dedicated her life to helping others in need at home and around the world," Obama said in a statement confirming the death of the American national.

"In Prescott, Arizona, she volunteered at a women's shelter and worked at an HIV/AIDS clinic. She worked with humanitarian organisations in India, Israel, and the Palestinian territories, compelled by her desire to serve others," he said.

He said the Kayla's compassion and dedication to assisting those in need shows that even amongst unconscionable evil, the essential decency of humanity can live on.

"ISIL is a hateful and abhorrent terrorist group whose actions stand in stark contrast to the spirit of people like Kayla," Obama added.

The IS group claimed last week that Mueller had been killed in an air strike by a Jordanian warplane in the Syrian city of Raqa, the militant group's self-proclaimed "capital."

Mourning the death, Secretary of State John Kerry said, "All Americans mourn the loss of Kayla Mueller, a compassionate young American who represented everything good about the human spirit."

"I have learned a great deal about Kayla through the stories shared about her during this awful period. She was someone any of us would be lucky to know as a daughter, sister, friend, or colleague.

"She so purposefully had one mission in life from the very start, and that was to help people: people in India, Israel, and the Palestinian Territories, people at an HIV/AIDS clinic and a women’s shelter at home in Arizona, and, most recently, Syrian refugees in Turkey," he said.

"While ISIL exploited the crisis in Syria to rule by violence and massacre the innocent, human tragedy moved Kayla to do the opposite. She embraced children who had lost their parents. She comforted the sick and the wounded. She gave people hope even as their world fell apart around them.

"Kayla's sense of values, her humanity and generosity, her idealism -- this is what will endure, and it will endure long, long after the barbarity of ISIL is defeated," Kerry said.