American aid worker Kayla Mueller - who was being held by Islamic State - has died, President Barack Obama has confirmed.
Ms Mueller's family said they were "heartbroken" at the news, and released a copy of a letter she had written in captivity.
Confirmation of Mueller's death comes days after Islamic State claimed the 26-year-old had died in a Jordanian air strike.
John Kerry and Chuck Hagel have expressed sadness at the death of US hostage Kayla Mueller who had been held by Islamic State.
Secretary of State Kerry said: "There are no words to express to Kayla's parents, Marsha and Carl, how sorry we are for their crushing loss, just how much so many wished for and worked to try and secure a better outcome.
"ISIL, and ISIL alone, is the reason Kayla is gone."
Hagel, the US secretary of defence, said: "The world is united in condemning ISIL's continued murder and imprisonment of innocents."
Earlier, President Obama vowed to "find and bring to justice the terrorists who are responsible" for the 26-year-old's death.
Following confirmation of the US hostage's death, Kayla Mueller's family have released a copy of a letter she wrote in captivity in 2014.
Here is what we know about American aid worker Kayla Mueller who was being held by Islamic State.