Obama vows justice after US hostage Kayla Mueller killed by Islamic State

US President Barack Obama yesterday 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".

“No matter how long it takes, the United States will find and bring to  justice the terrorists who are responsible for Kayla’s captivity and death,” Obama said in a statement.

Mueller's family also said in a statement that they were "heartbroken" to learn of her death and released a copy of a letter she had written in 2014 while in captivity.

The comments by Obama and the family come four days after the Islamic State said Mueller, a 26-year-old humanitarian worker, was killed on Friday when Jordanian fighter jets bombed a building where she was being held.

Mueller was determined to have been killed after her Islamic State captors reached out privately to her family over the weekend, a White House spokeswoman said.

IS sent  Mueller’s parents a “private message” with “additional information” which allowed the intelligence services to confirm her death, the White House and family said.

The Washington Post reported that Mueller’s family had been sent a  photograph of their daughter’s body.