Rod Stewart Mocks ISIS Beheading in Desert

Rod Stewart says he's sorry for mocking an ISIS beheading in the desert outside Abu Dhabi, but some outraged Brits think he should pay a higher price.

The video shows Rod, his wife, Penny, and friends climbing a sand dune. One of the friends gets on his knees in front of Rod ... who pretends to cut off the man's head.

Penny posted the video ... but deleted it a few hours later, after the immediate backlash started. 72-year-old Rod issued an apology, saying they were "larking about pre-show" and were "spontaneously playing out Game Of Thrones."

He added, "Understandably, this has been misinterpreted and I send my deepest apologies to those who have been offended.”

Angry British citizens have suggested online Stewart's Knighthood should be withdrawn.