The general leading the US-led war against Islamic State jihadists on Tuesday denounced the "savage" execution of a Jordanian pilot, who was purportedly shown being burned alive in a video released by the group.

The "vicious act" is yet another example of the IS group's "brutality and warped ideology," General Lloyd Austin, head of Central Command, said in a statement.

"US Central Command strongly condemns ISIL's savage murder" of Lieutenant Maaz al-Kassasbeh," he said.

Austin said he spoke with the chief of staff of Jordan's armed forces and "assured him that we stand with our Jordanian partners and together we will fight this barbaric enemy until it is defeated."