Kayla Mueller, 26, an American humanitarian worker from Prescott, Arizona is pictured in this undated handout photo. [Photo/Agencies]

WASHINGTON - The United States on Tuesday confirmed the death of an American female hostage held by the Islamic State (IS) militant group.

"It is with profound sadness that we have learned of the death of Kayla Jean Mueller," President Barack Obama said in a White House statement.

Mueller, a 26-year-old humanitarian aid worker, was captured in Syria in August 2013. IS last week claimed she had been killed in a Jordanian airstrike. However, US officials at the time said they could not confirm it.

"We are heartbroken to share that we've received confirmation that Kayla Jean Mueller, has lost her life," Mueller's parents said in a statement, "She dedicated the whole of her young life to helping those in need of freedom, justice, and peace."

The US officials right now could not confirm the cause of Mueller's death or when she died. But Obama pledged to "find and bring to justice the terrorists who are responsible for Kayla's captivity and death."