File Photo: A picture showing Islamic State militants. (Associated Press)
The United States on Friday said that it has not yet seen any proof to confirm a claim by the Islamic State group that a female American hostage has been killed in an air strike in Syria by a Jordanian plane.
"We are obviously deeply concerned by these reports. We have not at this time seen any evidence that corroborates ISIL's claim," said National Security Council spokeswoman Bernadette Meehan.
In a statement posted on jihadist websites, the IS group said the woman was buried beneath rubble after an air raid by a Jordanian warplane in Raqa.
The statement did not show any pictures of a body and there was no independent confirmation of her reported death.
The IS group has murdered both locals and foreigners, including two US journalists, an American aid worker, two British aid workers, two Japanese hostages and a Jordanian pilot.
Jordan, one of several Arab countries in the US-led coalition battling IS, vowed a harsh response after the jihadists released a gruesome video this week showing the burning alive of airman Maaz al-Kassasbeh.