She's still alive

The parents of a 26-year-old American who Islamic State extremists say was killed in an airstrike in Syria said in a statement addressed to group leaders that the claim of their daughter's death concerned them but they were still hopeful she was alive.

The Islamic State group said on Friday that Kayla Jean Mueller of Prescott, Arizona, died in a Jordanian airstrike, but the government of Jordan dismissed the statement as "criminal propaganda," and the US said it had not seen any evidence to corroborate the report.

Mueller is the only known remaining US hostage held by the Islamic State group.

If the death is confirmed, she would be the fourth American to die while being held by Islamic State militants. Three others — journalists James Foley and Steven Sotloff and aid worker Peter Kassig — were beheaded by the group.

"You told us that you treated Kayla as your guest, as your guest her safety and well-being remains your responsibility," Mueller's family said in a short statement released Friday.

Mueller is an aid worker who previously volunteered with organizations in India, Israel and the Palestinian territories. Her identity had not been disclosed until now out of fears for her safety. Her family said she was taken hostage by the Islamic State group on Aug. 4, 2013, while leaving a hospital in Syria.

"The common thread of Kayla's life has been her quiet leadership and strong desire to serve others," Mueller's family said.