The US State Department says it cannot confirm reports that a female American hostage has been killed in a recent air strike conducted in Syria.

Spokeswoman Marie Harf said the State Department acknowledged that some Americans were held abroad, including by the Islamic State (IS), but declined to provide additional information.

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IS militants claimed on Friday that an American female hostage was killed in an air strike by Jordan, according to jihadist tracking group SITE Intelligence.

In a statement posted on jihadist websites, IS said the woman was buried beneath the rubble after a raid by a Jordanian warplane in Raqqa, the self-proclaimed capital of the militant group.

“The plane from the crusader coalition bombed a position outside the city of Raqqa after Friday prayers,” it said.

“No fighter was wounded but we can confirm that an American hostage was killed in the strikes.”

The statement did not show any pictures of a body and there was no independent confirmation of her reported death.

IS jihadists have seized swathes of territory in Iraq and Syria, ruling with a brutal version of Islamic law.

The 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.