Members of the small Arizona town where Kayla Mueller grew up gathered in grief after learning that the aid worker who travelled the world to help others had died in the hands of Islamic State (IS) militants.

US President Barack Obama confirmed the death of Kayla Mueller, a US aid worker who had been held hostage by Islamic State militants, saying the United States would “find and bring to justice the terrorists who are responsible”.

Islamic State said yesterday that an American woman hostage it was holding in Syria was killed when Jordanian fighter jets bombed a building where she was being held, but Jordan expressed doubt about the Islamist militant group’s account of her death.